Dried Blood Spot Filter Paper Research Articles

Screening for Pompe Disease in High-Risk Pediatric Patients: Experience from a Tertiary Care Center in Rajasthan

AbstractA high index of suspicion is required to diagnose rare genetic disorders, such as Pompe disease, with common clinical manifestations in children. There is a need to sensitize physicians regarding cues to early screening and diagnosis of such patients. Minimal epidemiological data are available on Pompe disease in India. The aim of this study was to determine the prevalence of Pompe disease in high-risk pediatric populations and determine the appropriateness of screening dried blood spot (DBS) tests to facilitate the diagnosis of Pompe disease. We screened pediatric patients presented with (1) unexplained hypotonia, respiratory distress, cardiomyopathy, and elevated liver function tests; and (2) unexplained limb girdle muscle weakness through a DBS test for enzyme assay. Those patients found positive underwent acid alpha-glucosidase mutational analysis. This prospective cross-sectional study was conducted in 45 suspected patients after approval from the institutional ethical committee. Of the 45 suspected patients, 9 (20%) were found to be positive by DBS test. Out of these nine tested, four (44.4%) were positive, two (22.2%) were negative, and three (33.3%) could not be tested for mutation analysis. The prevalence of genetically confirmed Pompe disease in high-risk populations was 8.8%. The results of this study show that clinical suspicion and DBS filter paper test facilitate early diagnosis and management, thereby improving the quality of life in patients. DBS test acts as a robust, rapid first-tier screening test for Pompe disease.

Updated Confirmatory Diagnosis for Mucopolysaccharidoses in Taiwanese Infants and the Application of Gene Variants

Mucopolysaccharidosis (MPS) is a lysosomal storage disease caused by genetic defects that result in deficiency of one specific enzyme activity, consequently impairing the stepwise degradation of glycosaminoglycans (GAGs). Except for MPS II, the other types of MPS have autosomal recessive inheritance in which two copies of an abnormal allele must be present in order for the disease to develop. In this study, we present the status of variant alleles and biochemistry results found in infants suspected of having MPS I, II, IVA, and VI. A total of 324 suspected infants, including 12 for MPS I, 223 for MPS II, 72 for MPS IVA, and 17 for MPS VI, who were referred for MPS confirmation from newborn screening centers in Taiwan, were enrolled. In all of these infants, one specific enzyme activity in dried blood spot filter paper was lower than the cut-off value in the first blood sample, as well asin a second follow-up sample. The confirmatory methods used in this study included Sanger sequencing, next-generation sequencing, leukocyte enzyme fluorometric assay, and GAG-derived disaccharides in urine using tandem mass spectrometry assays. The results showed that five, nine, and six infants had MPS I, II, and IVA, respectively, and all of them were asymptomatic. Thus, a laboratory diagnosis is extremely important to confirm the diagnosis of MPS. The other infants with identified nucleotide variations and reductions in leukocyte enzyme activities were categorized as being highly suspected cases requiring long-term and intensive follow-up examinations. In summary, the final confirmation of MPS depends on the most powerful biomarkers found in urine, i.e., the quantification of GAG-derived disaccharides including dermatan sulfate, heparan sulfate, and keratan sulfate, and analysis of genetic variants can help predict outcomes and guide treatment.

Dried blood spot (DBS) for ethyl glucuronide (EtG) and ethyl sulfate (EtS) determination in blood with a new design of “volumetric” DBS filter paper card

Determination of EtG in blood can be performed from capillary blood with high sensitivity and detection limits of down to 1 ng/mL for EtG–and in addition to phosphatidyl ethanol (PEth) determination, EtG concentrations can be used for interpretation of consumption habits of patients in maintenance therapy. Sampling of capillary blood is a crucial preanalytical step–and different methods have been suggested for collection of a defined volume (VAMS, Capitainer, HemaXis, and capillaries for collection of samples). We used and validated a new volumetric capillary blood sampling card (DBSv cards, Protzek, Lörrach/Germany) which can be used either for self-sampling of dried blood spots (up to 4 times 20 microliter of blood) on filter paper with convenient handling by the patients or also in laboratory work. In contrast to standard DBS cards with printed circles on a filter paper, a newly designed card with a paper comb with four teeth per card, which allows a volumetric collection of 20 microlitres of blood per tooth, was used. Venous blood was pipetted on the teeth of DBSv cards, dried, and one paper tooth was ripped off and extracted by adding 490 microliter of methanol and 10 microliter of ISTD (400 ng/ml D5-EtG and 400 ng/ml D5-EtS). The samples were then vortexed for 5 minutes and centrifuged for 10 minutes. After transferring them into vials, the solutions were evaporated under a stream of nitrogen and reconstituted in 80 microliter of a water/0.1% formic acid. The samples were shaken and 10 μL were injected onto the LC column. A previously published LC-MS/MS method was adapted for a QTrap 5500 triple-quadrupole ion trap mass spectrometer (Sciex, Toronto, Canada) with an Acquity C18 HSS T3 column (Waters, Wexford, Ireland) and detection of EtG, D5-EtG, EtS and D5-EtS was performed according to forensic guidelines using one precursor and two product ions. Lower limits of quantification were 10 ng/mL for EtG and 20 ng/mL for EtS–with linear ranges of 10 to 5000 ng/mL for EtG and (50 to 2500 ng/mL for EtS. Traces of EtS were found in HPLC grade solvent, and a solvent selection between products of different manufacturers had to be performed. One brand methanol showed the lowest baseline level of EtS, which was in the range of 20 ng/mL. Thus, for determination of EtS, a lower limit of quantitation of 50 ng/mL was defined, whereas EtG could be quantified at concentrations above 10 ng/mL. A validation with spiked blood samples was performed. Samples from forensic cases and from drinking studies, where DBS were collected for the analysis of alcohol biomarkers (PEth and EtG/EtS) have been analyzed. The dried blood spot sample collection in laboratory or by self-sampling (of capillary blood) can be used to detect EtG and EtS at very low levels. The results show the potential of DBS analysis for alcohol markers EtG and EtS–which can be used for abstinence monitoring by very low limits of detection, especially for EtG, or for the detection of a recent alcohol consumption, when ethanol has already been eliminated from the body. A contamination of pure HPLC-grade solvent methanol was found for EtS determination, this has to be kept in mind, and needs further optimization for detection of EtS at lower concentrations in biological samples.

Detecting asymptomatic carriage of Plasmodium falciparum in southern Ghana: utility of molecular and serological diagnostic tools

BackgroundAsymptomatic malaria infections can serve as potential reservoirs for malaria transmission. The density of parasites contained in these infections range from microscopic to submicroscopic densities, making the accurate detection of asymptomatic parasite carriage highly dependent on the sensitivity of the tools used for the diagnosis. This study sought to evaluate the sensitivities of a variety of molecular and serological diagnostic tools at determining the prevalence of asymptomatic Plasmodium falciparum parasite infections in two communities with varying malaria parasite prevalence.MethodsWhole blood was collected from 194 afebrile participants aged between 6 and 70 years old living in a high (Obom) and a low (Asutsuare) malaria transmission setting of Ghana. Thick and thin blood smears, HRP2 based malaria rapid diagnostic test (RDT) and filter paper dried blood spots (DBS) were prepared from each blood sample. Genomic DNA was extracted from the remaining blood and used in Plasmodium specific photo-induced electron transfer polymerase chain reaction (PET-PCR) and Nested PCR, whilst the HRP2 antigen content of the DBS was estimated using a bead immunoassay. A comparison of malaria parasite prevalence as determined by each method was performed.ResultsParasite prevalence in the high transmission site of Obom was estimated at 71.4%, 61.9%, 60%, 37.8% and 19.1% by Nested PCR, the HRP2 bead assay, PET-PCR, HRP2-RDT and microscopy respectively. Parasite prevalence in the low transmission site of Asutsuare was estimated at 50.1%, 11.2%, 5.6%, 0% and 2.2% by Nested PCR, the HRP2 bead assay, PET-PCR, RDT and microscopy, respectively. The diagnostic performance of Nested PCR, PET-PCR and the HRP2 bead assay was similar in Obom but in Asutsuare, Nested PCR had a significantly higher sensitivity than PET-PCR and the HRP2 bead assay, which had similar sensitivity.ConclusionsNested PCR exhibited the highest sensitivity by identifying the highest prevalence of asymptomatic P. falciparum in both the high and low parasite prevalence settings. However, parasite prevalence estimated by the HRP2 bead assay and PET-PCR had the highest level of inter-rater agreement relative to all the other tools tested and have the advantage of requiring fewer processing steps relative to Nested PCR and producing quantitative results.

Polymorphisms in Plasmodium falciparum dihydropteroate synthetase and dihydrofolate reductase genes in Nigerian children with uncomplicated malaria using high-resolution melting technique

In 2005, the Nigerian Federal Ministry of Health revised the treatment policy for uncomplicated malaria with the introduction of artemisinin-based combination therapies (ACTs). This policy change discouraged the use of Sulphadoxine-pyrimethamine (SP) as the second-line treatment of uncomplicated falciparum malaria. However, SP is used as an intermittent preventive treatment of malaria in pregnancy (IPTp) and seasonal malaria chemoprevention (SMC) in children aged 3–59 months. There have been increasing reports of SP resistance especially in the non-pregnant population in Nigeria, thus, the need to continually monitor the efficacy of SP as IPTp and SMC by estimating polymorphisms in dihydropteroate synthetase (dhps) and dihydrofolate reductase (dhfr) genes associated with SP resistance. The high resolution-melting (HRM) assay was used to investigate polymorphisms in codons 51, 59, 108 and 164 of the dhfr gene and codons 437, 540, 581 and 613 of the dhps gene. DNA was extracted from 271 dried bloodspot filter paper samples obtained from children (< 5 years old) with uncomplicated malaria. The dhfr triple mutant I51R59N108, dhps double mutant G437G581 and quadruple dhfr I51R59N108 + dhps G437 mutant haplotypes were observed in 80.8%, 13.7% and 52.8% parasites, respectively. Although the quintuple dhfr I51R59N108 + dhps G437E540 and sextuple dhfr I51R59N108 + dhps G437E540G581 mutant haplotypes linked with in-vivo and in-vitro SP resistance were not detected, constant surveillance of these haplotypes should be done in the country to detect any change in prevalence.

Glucose-6-phosphate dehydrogenase enzyme stability in filter paper dried blood spots

ObjectivePrior to initial distribution of Glucose-6-phosphate dehydrogenase (G6PD) proficiency testing (PT) materials, we evaluated G6PD enzyme stability in dried blood spots (DBS) under various temperature and humidity environments to develop storage and usage guidelines for our new materials. Design & methodsWe prepared fresh G6PD-normal DBS materials and conducted stability evaluations of daily use and short and long-term storage under various temperature and humidity environments. ResultsG6PD DBS PT materials retained 92% of initial activity after 30days of use at 4°C. Materials stored at −20°C and 4°C with desiccant for 30days retained 95% and 90% of initial activity, respectively. When stored for one year at −20°C or six months at 4°C specimens retained >90% of initial activity. Specimens stored at 37°C with desiccant lost 10% activity in three days. At the end of 30days, specimens stored under ‘Extreme’—humidity >50% without desiccant— conditions at 37°C assayed below the NSQAP cut off for G6PD. Humidity exacerbated loss of enzyme activity with increasing temperature and time duration. ConclusionData suggest that G6PD PT materials can be stored at 4°C and used for up to one month and can be stored at −20°C for one year and yield >90% enzyme activity. Exposure to warm temperatures, especially with elevated humidity, should be avoided. Desiccant should always be used to mitigate humidity effects.

Dried Blood Spot Technique for the Monitoring of Ambrisentan, Bosentan, Sildenafil, and Tadalafil in Patients with Pulmonary Arterial Hypertension.

Endothelin receptor antagonists (ERA) and phosphodiesterase 5 inhibitors (PDE5I) are long-term therapeutics for the treatment of pulmonary arterial hypertension (PAH). Their interindividual pharmacokinetic variability is remarkably large, and despite the seriousness of the disease, nonadherence is occurring. Therefore, methods to monitor sufficient circulating drug levels are essential. The objectives of this study were to develop and validate dried blood spot (DBS) assays for the quantification of ambrisentan, bosentan, sildenafil, tadalafil, and their main metabolites. We also quantified the influence of different hematocrit levels and assessed the correlation of simultaneously taken capillary whole blood (DBS) and venous plasma samples. The aliquot punches were extracted by liquid/liquid extraction followed by liquid chromatography/tandem mass spectrometry (LC/MS/MS) quantification methods. All assays fulfilled the requirements of the FDA and EMA guidelines for assay validation with a lower limit of quantification of 2.5 ng/mL for the ERAs, 5 ng/mL for sildenafil, and 10 ng/mL for tadalafil. All analytes were stable for at least 147 days when stored on DBS filter paper cards at room temperature in the dark. Due to poor distribution into erythrocytes, drug concentrations in DBS were always lower than in plasma, resulting in conversion factors of 1.58 for ambrisentan and sildenafil and 1.52 for bosentan and tadalafil.

17-hydroxyprogesterone quantification in dried blood spots by high performance liquid chromatography-tandem mass spectroscopy

Measurement of 17-hydroxyprogesterone (17-OHP) in daily dried blood spot profiles via radioimmunoassay is a convenient and accepted method for monitoring of glucocorticoid therapy in Congenital Adrenal Hyperplasia. Characteristics of this method that serve to limit its clinical usefulness include its lack of specificity for 17-OHP, and a relatively high limit of detection. Mass Spectroscopy is the gold standard method for steroid quantification. We aim to establish a High Performance Liquid Chromatography-Tandem Mass Spectroscopy (HPLC-MS/MS) method for dried blood spot 17-OHP quantification and develop normative age- and tanner-specific, as well as Congenital Adrenal Hyperplasia genotype-phenotype correlated reference ranges to guide glucocorticoid therapy. Four 3mm blood spots were punched from patient dried blood spot filter paper specimens. 17-OHP was eluted into solvent and concentrated using liquid nitrogen. Steroids were separated using high performance liquid chromatography and quantitated by Tandem Mass Spectrometry. For the radioimmunassay / HPLC-MS/MS correlations, measurements were performed by both methods on 49 samples from children with glucocorticoid-dependent Congenital Adrenal Hyperplasia, as well as children undergoing dynamic endocrine function testing at The Mater Children’s Hospital. Reference samples for HPLC-MS/MS calibration, and determination of sensitivity, precision, and recovery were prepared using whole blood samples spiked with 17-OHP spotted onto filter paper. Concentrations were expressed as mean (nmol/L), standard deviation, and coefficient of variation (%). There was excellent correlation between HPLC-MS/MS and radioimmunoassay methods (r2=0.9610). For the radioimmunoassay method, the lower limit of quantification has been established at <5 nmol/L while LC-MS/MS allows detection to 1.0 nmol/L (1.2nmol/L, 0.26, 22%) with a proposed lower limit of quantification of 1.5 nmol/L (1.3 nmol/L, 1.3, 13%). We have established an accurate, reliable, and specific method for quantifying 17-OHP concentrations from dried blood spot using HPLC-MS/MS. This will allow for the establishment of clinically relevant and time-specific reference ranges to guide glucocorticoid dose adjustment in children with Congenital Adrenal Hyperplasia.

Pilot study for the neonatal screening of congenital T cell lymphopenias

Pilot study for the neonatal screening of congenital T cell lymphopenias

Trends in chloroquine resistance marker, Pfcrt-K76T mutation ten years after chloroquine withdrawal in Tanzania

BackgroundPlasmodium falciparum resistance to anti-malarial drugs remains a major obstacle to the control of malaria. In 2001 Tanzania replaced chloroquine (CQ) with sulphadoxine-pyrimethamine (SP) as first-line drug, which in turn was replaced by artemisinin combination therapy in 2006. SP has however, continued to be used in intermittent preventive treatment of malaria in pregnancy (IPTp) despite reports of high levels of resistance to SP due to the lack of alternatives to SP for IPTp. Recent reports have indicated recovery of CQ-susceptibility in Malawi, Kenya, Mozambique, and Tanzania based on the prevalence of wild types at codon 76 of the Pfcrt gene in indigenous P. falciparum populations. The current prevalence of this Pfcrt-76 CQ resistance marker from six regions of Tanzania mainland is hereby reported.MethodsDNA extracted from filter-paper dried blood spots and rapid diagnostics kit strips collected from finger-prick blood were used to genotype the Pfcrt-76 resistance marker using PCR-RFLP. Data from previously published studies were used to generate CQ susceptibility recovery trends using logistic regression model.ResultsSeven hundred and forty one (741) samples were genotyped. The current frequency of the CQ-susceptible Pfcrt-K76 was above 92% and did not differ between regions in Tanzania (χ2 = 2.37; p = 0.795). The K76 allelic prevalence was between 85.7 and 93% in regions (χ2 = 7.88, p = 0.163). The CQ resistance recovery trends showed regional variability that may be caused by differences in malaria transmission intensity, but overall the trends converge as the susceptibility levels in all regions approach >90%.ConclusionsCQ withdrawal in Tanzania has resulted into >90% recovery of susceptibility in ten years of withdrawal. These findings are in support of the search for CQ-based combination drugs as a possible future alternative to SP for IPTp in places where full recovery of CQ-susceptibility will be evident.

DNA methylome profiling using neonatal dried blood spot samples: A proof-of-principle study

DNA methylation is the most common DNA modification and perhaps the best described epigenetic modification. It is believed to be important for genomic imprinting and gene regulation and has been associated with the development of diseases such as schizophrenia and some types of cancer.Neonatal dried blood spot samples, commonly known as Guthrie cards, are routinely collected worldwide to screen newborns for diseases. Some countries, including Denmark, have been storing the excess neonatal dried blood spot samples in biobanks for decades. Representing a high percentage of the population under a certain age, the neonatal dried blood spot samples are a potential alternative to collecting new samples to study diseases. As such, neonatal dried blood spot samples have previously been used for DNA genotyping studies with excellent results. However, the amount of material available for research is often limited, challenging researchers to generate the most data from a limited quantity of material.In this proof-of-principle study, we address whether two 3.2mm disks punched from a neonatal dried blood spot sample contain enough DNA for genome-wide methylome profiling, measuring 27,578 loci at the same time. We selected two subjects and carried out the following with each: 1) collected an adult whole-blood sample as reference, 2) spotted a fraction of the whole-blood sample onto a similar type of filter paper as used in the newborn screening and stored it for 3years to serve as a dried blood spot reference, and 3) identified the archived neonatal dried blood spot samples, stored for 26–28years, in the Danish Newborn Screening Biobank as a representative of the archived samples. For comparison, we used two different kits for DNA extraction.The DNA, extracted using the Extract-N-Amp Blood PCR kit, was analyzed, and no statistically significant differences were observed (P<0.001) when we compared the methylation profile of the reference whole-blood samples to the dried blood spot references. This indicates that two 3.2mm disks contain enough material for reliable methylome profiling and that storing the whole-blood sample on neonatal dried blood spot filter paper for 3years does not interfere with the outcome of the analysis.Furthermore, we compared the adult DNA methylation profile to the neonatal dried blood spot sample profile. Approximately 50 sites in the subjects were significantly (P<0.001) different in the newborn sample compared with the adult sample. Both being healthy adults and the high quality of the DNA methylation array led to the conclusion that the archived neonatal dried blood spot samples can be used for methylome profiling, despite decades of storage and DNA degradation.In conclusion, we show that reliable methylome data can be obtained from old neonatal dried blood spot samples, by using a reasonable amount of the limited resource. This further adds to the use of neonatal dried blood spot samples in genetic research and screening and paves the way for unique population-based studies of epigenetic modifications after birth.

Early diagnosis of congenital toxoplasmosis in newborn infants using IgG subclasses against two Toxoplasma gondii recombinant proteins

The aim of this work was to evaluate the utility of ELISA-based testing of total IgG (IgGt) antibodies and its subclasses (IgG1, IgG2, IgG3 and IgG4) against soluble (STAg) and recombinant (rSAG1 and rMIC3) antigens of Toxoplasma gondii for diagnosing congenital toxoplasmosis. Sera from 217 newborns initially testing positive for specific IgM in filter paper dried blood spots were tested for specific IgM and IgG by ELFA-VIDAS. Congenital toxoplasmosis was confirmed in 175 and ruled out in 42 infants. The validity of the ELISA tests was determined using the persistence of IgG antibodies (ELFA-VIDAS kit) at the end of 12 months, which is considered the reference test for the diagnosis of congenital toxoplasmosis. The frequency of positivity with IgGt against STAg, rSAG1 and rMIC3 was found in 97.2%, 96.3% and 80.2%, respectively, of the newborns with confirmed congenital toxoplasmosis. IgG1 reacted with all three antigens, while IgG3 and IgG4 reacted preferentially with rMIC3. Higher mean values of reactivity (sample optical density/cut-off) were found for all subclasses when using rMIC3. All of the antigens showed high sensitivity and low specificity in detecting anti-T. gondii IgGt and IgG1 and low sensitivity and high specificity in detecting IgG3 and IgG4. In conclusion, the combined detection of IgG antibody subclasses against recombinant toxoplasmic antigens may be useful for the early diagnosis of congenital toxoplasmosis.

Stability of gametocyte-specific Pfs25-mRNA in dried blood spots on filter paper subjected to different storage conditions

BackgroundReal-time quantitative nucleic acid sequence-based amplification (QT-NASBA) is a sensitive method for detection of sub-microscopic gametocytaemia by measuring gametocyte-specific mRNA. Performing analysis on fresh whole blood samples is often not feasible in remote and resource-poor areas. Convenient methods for sample storage and transport are urgently needed.MethodsReal-time QT-NASBA was performed on whole blood spiked with a dilution series of purified in-vitro cultivated gametocytes. The blood was either freshly processed or spotted on filter papers. Gametocyte detection sensitivity for QT-NASBA was determined and controlled by microscopy. Dried blood spot (DBS) samples were subjected to five different storage conditions and the loss of sensitivity over time was investigated. A formula to approximate the loss of Pfs25-mRNA due to different storage conditions and time was developed.ResultsPfs25-mRNA was measured in time to positivity (TTP) and correlated well with the microscopic counts and the theoretical concentrations of the dilution series. TTP results constantly indicated higher amounts of RNA in filter paper samples extracted after 24 hours than in immediately extracted fresh blood. Among investigated storage conditions freezing at −20°C performed best with 98.7% of the Pfs25-mRNA still detectable at day 28 compared to fresh blood samples. After 92 days, the RNA detection rate was only slightly decreased to 92.9%. Samples stored at 37°C showed most decay with only 64.5% of Pfs25-mRNA detectable after one month. The calculated theoretical detection limit for 24 h-old DBS filter paper samples was 0.0095 (95% CI: 0.0025 to 0.0380) per μl.ConclusionsThe results suggest that the application of DBS filter papers for quantification of Plasmodium falciparum gametocytes with real-time QT-NASBA is practical and recommendable. This method proved sensitive enough for detection of sub-microscopic densities even after prolonged storage. Decay rates can be predicted for different storage conditions as well as durations.

Easy Diagnosis of Invasive Pneumococcal Disease

To the Editor: Invasive pneumococcal disease (IPD) causes many cases of severe disease and death among children <5 years of age, mostly in developing countries (1,2). Before conjugate vaccines can be introduced in developing countries, information about disease epidemiology is urgently needed. The lack of laboratories equipped to perform pneumococcal serotyping leads to the need to send isolates to reference laboratories. Good sample preservation is necessary to prevent samples from arriving at the laboratory in poor condition. We evaluated the usefulness of multiplex real-time PCR from strains and blood samples kept at room temperature on dried blood spot (DBS) filter paper for detecting and serotyping Streptococcus pneumoniae. DBS screening is a reliable method that requires only a small amount of blood; it is used for the diagnosis of several human diseases (3,4). To validate the technique, we selected 15 pneumococcus clinical isolates representing 15 serotypes (1, 5, 19A, 19F, 14, 3, 7F, 4, 6A, 6B, 8, 9N, 18C, 23A, 23F) obtained during 2009 from patients at Hospital Sant Joan de Deu, in Barcelona. These isolates, used as controls, had been serotyped by quellung reaction at the Instituto de Salud Carlos III, Majadahonda-Madrid, Spain. These strains were cultured overnight at 35°C in 5% carbon dioxide on Columbia agar plates with 5% sheep blood (bioMerieux SA, Marcy l’Etoile, France). A suspension of each strain was adjusted to match a 0.5 McFarland standard (equivalent to 108 colony-forming units (CFU)/mL). Stock solutions of pneumococcus culture for each previously identified serotype were injected into blood previously extracted from 2 healthy volunteers. Serial dilutions of 100,000 CFU/mL to 1,000 CFU/mL (1,000 to 10 CFU equivalents/PCR) were performed. A total of 100 µL of blood was applied to DBS filter paper, and another 100 µL was used for DNA extraction from fresh blood. All DBS samples were air dried for 1 week. The procedure was also performed on negative control blood samples. DNA was extracted from DBS and fresh blood samples by using the NucliSense easyMAG automated extraction platform (bioMerieux, Boxtel, the Netherlands) according to the manufacturer’s instructions. DNA detection of the pneumolysin (ply) gene by real-time PCR was performed according to a published assay (5). In addition, we performed a multiplex real-time PCR for molecular serotype detection of serotypes 1, 3, 5, 4, 6A, 6B, 7FA, 8, 9VANL, 14, 15BC, 18CB, 19A, 19FBC, 23F, 23A and the conserved capsular gene wzg as described by Tarrago et al. (6). DNA extracts were amplified with the Applied Biosystems 7300 Real-time PCR System (Applied Biosystems, Foster City, CA, USA). Negative results were defined as those with cycle threshold >40. To evaluate the reliability obtained with this in vivo approach, we performed identification and serotyping of S. pneumoniae in 25 DBS samples from 25 children at Saint John of God Hospital in Mabesseneh-Lunsar, Sierra Leone. This hospital does not perform blood cultures. IPD was confirmed when DNA of a pneumolysin (ply) gene and an additional capsular gene of S. pneumoniae were detected by multiplex real-time PCR of DBS samples. Detection of ply, wzg, and the specific gene for molecular serotype showed that both fresh blood and DBS samples yielded correctly positive results from the 10-fold serial dilutions analyzed (Table). With respect to the 25 (11 female and 14 male) patients from Sierra Leone who had suspected IPD, the median age was 25.71 months (range 15 days to 96 months); all had a diagnosis of fever without apparent source, and 16 also had malaria. Of these 25 children, DBS samples from 15 (60%) yielded a positive result for the ply and wzg genes, so they were considered confirmed episodes of IPD. A serotype included in 13-valent conjugate vaccine was detected in 6 (40%) of 15 positive samples: serotypes 3, 7FA, 19A, 6A, 6B, and 9VNL (1 sample each). In the remaining 9 samples, the results for ply gene and wzg gene were positive, but none of the 24 tested serotypes was detected. Table Sensitivity of real-time PCR for detecting Streptococcus pneumoniae ply or wzg genes or a specific gene for molecular serotype from fresh or dried blood spot samples* This preliminary study enabled us to demonstrate that DBS screening is a reliable and easy method for diagnosing IPD and also for epidemiologic surveillance of the more frequent serotypes. The main limitation of our study is the small number of DBS samples sent from Saint John of God Hospital in Sierra Leone. In conclusion, the DBS technique enables reproducible transport of samples for identification and serotyping of S. pneumoniae by multiplex PCR. The use of DBS on filter paper is an attractive alternative method for storing samples at room temperature and easily transporting them. Additional studies, including evaluation of the relative sensitivity of this method compared to direct culture, are necessary.

Evaluation of a single round polymerase chain reaction assay using dried blood spots for diagnosis of HIV-1 infection in infants in an African setting

BackgroundThe aim of this study was to develop an economical 'in-house' single round polymerase chain reaction (PCR) assay using filter paper-dried blood spots (FP-DBS) for early infant HIV-1 diagnosis and to evaluate its performance in an African setting.MethodsAn 'in-house' single round PCR assay that targets conserved regions in the HIV-1 polymerase (pol) gene was validated for use with FP-DBS; first we validated this assay using FP-DBS spiked with cell standards of known HIV-1 copy numbers. Next, we validated the assay by testing the archived FP-DBS (N = 115) from infants of known HIV-1 infection status. Subsequently this 'in-house' HIV-1 pol PCR FP-DBS assay was then established in Nairobi, Kenya for further evaluation on freshly collected FP-DBS (N = 186) from infants, and compared with findings from a reference laboratory using the Roche Amplicor® HIV-1 DNA Test, version 1.5 assay.ResultsThe HIV-1 pol PCR FP-DBS assay could detect one HIV-1 proviral copy in 38.7% of tests, 2 copies in 46.9% of tests, 5 copies in 72.5% of tests and 10 copies in 98.1% of tests performed with spiked samples. Using the archived FP-DBS samples from infants of known infection status, this assay was 92.8% sensitive and 98.3% specific for HIV-1 infant diagnosis. Using 186 FP-DBS collected from infants recently defined as HIV-1 positive using the commercially available Roche Amplicor v1.5 assay, 178 FP-DBS tested positive by this 'in-house' single-round HIV-1 pol PCR FP-DBS PCR assay. Upon subsequent retesting, the 8 infant FP-DBS samples that were discordant were confirmed as HIV-1 negative by both assays using a second blood sample.ConclusionsHIV-1 was detected with high sensitivity and specificity using both archived and more recently collected samples. This suggests that this 'in-house' HIV-1 pol FP-DBS PCR assay can provide an alternative cost-effective, reliable and rapid method for early detection of HIV-1 infection in infants.

A method for lactate and pyruvate determination in filter-paper dried blood spots

Lactic acidemia is commonly associated with severe diseases in pediatric patients. Quantitation of blood lactate and pyruvate is important for the diagnosis and clinical management. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using dried blood spots (DBS) was developed and could be used for simultaneous quantification of blood lactate and pyruvate. The applicability of the developed method was tested and confirmed by the regression analysis between LC-MS/MS method and enzymatic assay. Lactate and pyruvate were extracted from DBS obtained from 580 full-term, 120 pre-term infants (gestations ranging from 24 to 36 weeks), and 65 patients with suspected lactic acidemia, with methanolic internal standard (IS) solutions of sodium L-lactate-(13)C(3) and pyruvate-(13)C(3). An API-2000 LC-MS/MS system with multiple reaction monitoring (MRM) mode was applied. The within-run and between-run precisions (CV%) were determined and the results were 1.9% and 3.9% for lactate (n=20) and 5.7% and 7.3% for pyruvate (n=20). The linearity of lactate (r=0.9986) and pyruvate (r=0.9973) based on the IS was excellent. The parameter r squared (r(2)) of linear regression between LC-MS/MS method and enzymatic assay was 0.9405 for lactate and 0.9447 for pyruvate, respectively, and the agreement between these methods was consistent and acceptable. The stability of lactate and pyruvate on DBS was also confirmed. The LC-MS/MS method we developed is a specific, sensitive, and reproducible method for measuring blood lactate and pyruvate concentrations. The use of DBS in this method makes it particularly attractive for pediatric patients.

Congenital toxoplasmosis and DALYs in the Netherlands

The calculation of disability-adjusted life years (DALYs) enables public health policy makers to compare the burden of disease of a specific disease with that of other (infectious) diseases. The incidence of a disease is important for the calculation of DALYs. To estimate the incidence of congenital toxoplasmosis (CT), a random sample of 10,008 dried blood spot filter paper cards from babies born in 2006 in the Netherlands were tested for Toxoplasma gondii-specific IgM antibodies. Eighteen samples were confirmed as positive for IgM, resulting in an observed birth incidence of CT of 1.8 cases per 1,000 live-born children in 2006 and an adjusted incidence of 2.0 cases per 1,000. This means that 388 infected children were born in 2006. The most likely burden of disease is estimated to be 2,300 DALYs (range 820-6,710 DALYs). In the previous calculations, using data from a regional study from 1987, this estimate was 620 DALYs (range 220-1,900 DALYs). The incidence of CT in the Netherlands is much higher than previously reported; it is 10 times higher than in Denmark and 20 times higher than in Ireland, based on estimates obtained using the same methods. There is no screening program in the Netherlands; most children will be born asymptomatic and therefore will not be detected or treated.

Anderson-Fabry disease: a case-finding study among male kidney transplant recipients in Austria

The diagnosis of Anderson-Fabry disease is often delayed or even missed. As severe renal manifestations are a hallmark of alfa-galactosidase A (AGAL) deficiency, we tested the hypothesis that Anderson-Fabry disease is under-recognized among male kidney transplant recipients. This nation-wide study in Austria enrolled 1306 patients (ca 65% of all kidney transplanted males) from 30 kidney centers. AGAL activity was determined from filter paper dried blood spots by a fluorescence assay. A positive screening test was defined by an AGAL activity below 1.5 nmol/h/ml. In patients with a positive blood spot-screening test, AGAL activity was re-examined in peripheral blood leukocytes. Genetic testing for mutations in the GLA gene was performed by sequencing to confirm the diagnosis of Anderson-Fabry disease. Two previously not recognized cases with Anderson-Fabry disease were identified. Our study is the first showing that a diagnosis of Anderson-Fabry disease can be missed even in patients who undergo kidney transplantation. Case-finding strategies may be considered a useful tool for diagnosis of this rare disease that may be somewhat more prevalent among kidney transplant recipients compared with dialysis populations.

A rapid semi automated method for DNA extraction from dried-blood spots: Application to the HLA-DR shared epitope analysis in rheumatoid arthritis

Genomic DNA extraction for genotyping analysis is performed from blood samples and is time consuming. We describe a more rapid DNA extraction method, “DBS-miniMAG”, that combines filter paper dried blood spots (DBS) with the NucliSens® miniMAG™ semi-automated instrument (bioMérieux). To assess the performance of this method, a post-PCR HLA-DR shared epitope (SE) oligotyping assay was used as a read-out in a cohort of 72 arthritis patients. This new method was compared to the standard manual DBS extraction protocol using FTA® reagents (Whatmann Bio-Science), and to a reference phenol-chloroform-based method using EDTA whole blood samples. Higher yield of PCR amplicons was observed with DNA extracts obtained using “DBS-miniMAG” method. The intra- and inter-assay variability of the “DBS-miniMAG” method was similar to that obtained with “DBS-FTA” washing process. Concerning the HLA-DR SE genotyping, “DBS-miniMAG” and “DBS-FTA” methods gave 100% concordance compared to the reference phenol-chloroform method. More importantly, the hands-on time and the turnaround time for “DBS-miniMAG” were both two-times shorter than for “DBS-FTA” protocol. Therefore, the “DBS-miniMAG” combination could facilitate polymorphism analysis in routine clinical practice and the creation of large DNA banks using very small amounts of blood.

Evaluation of the dried blood spot filter paper technology and five testing strategies of HIV-1 and HIV-2 infections in West Africa

Simple robust approaches are needed to monitor the prevalence and incidence of HIV in Africa. The aim of this study was to evaluate the use of dried blood spot (DBS) as an alternative to serum or plasma for sentinel surveillance. Paired DBS and blood samples were obtained from 200 patients attending a genito-urinary medicine clinic in West Africa. The gold standard of diagnosis was based on the combination of 3 enzyme-linked immunosorbent assays (ELISA) using serum. The presence of HIV antibodies in eluates of dried blood spots was detected by ELISA, Gelatin Particle Assay (GPA) and Pepti-Lav 1-2 in 5 different testing strategies. All 200 eluates were tested individually, and in addition pools of 5 eluates each were tested. The sensitivity of the testing strategies ranged from 95.0% (83.1 - 99.4%) to 100% and the specificity from 97.5% (93.7 - 99.3%) to 100%. Testing in pools of 5 did not affect sensitivity. Dried blood spots were easy to work with. Test kit and laboratory consumable costs varied between 492 pounds and 1037 pounds (unpooled strategies) and 163 pounds and 421 pounds (pooled). The monospecific ELISAs used in this study are no longer in production; currently available differentiating assays need to be tested. DBS are recommended for sentinel surveillance in Africa.