Finger-prick Samples Research Articles

Comparison of Venous and Capillary Differential Leukocyte Counts Using a Standard Hematology Analyzer and a Novel Microfluidic Impedance Cytometer

Capillary blood sampling has been identified as a potentially suitable technique for use in diagnostic testing of the full blood count (FBC) at the point-of-care (POC), for which a recent need has been highlighted. In this study we assess the accuracy of capillary blood counts and evaluate the potential of a miniaturized cytometer developed for POC testing. Differential leukocyte counts in the normal clinical range from fingerprick (capillary) and venous blood samples were measured and compared using a standard hematology analyzer. The accuracy of our novel microfluidic impedance cytometer (MIC) was then tested by comparing same-site measurements to those obtained with the standard analyzer. The concordance between measurements of fingerprick and venous blood samples using the standard hematology analyzer was high, with no clinically relevant differences observed between the mean differential leukocyte counts. Concordance data between the MIC and the standard analyzer on same-site measurements presented significantly lower leukocyte counts determined by the MIC. This systematic undercount was consistent across the measured (normal) concentration range, suggesting that an internal correction factor could be applied. Differential leukocyte counts obtained from fingerprick samples accurately reflect those from venous blood, which confirms the potential of capillary blood sampling for POC testing of the FBC. Furthermore, the MIC device demonstrated here presents a realistic technology for the future development of FBC and related tests for use at the site of patient care.

Lymphatic filariasis among the Yakurr people of Cross River State, Nigeria

BackgroundIn order to initiate a disease elimination programme for lymphatic filariasis based on mass drug administration, a proper understanding of the geographical distribution and degree of risk is essential.MethodsAn investigation of lymphatic filariasis due to Wuchereria bancrofti was carried out among 785 people in four communities of Yakurr Local Government Area of Cross River State, Nigeria between March and August, 2009. Finger prick blood smear samples collected from the subjects were examined for W. bancrofti using standard parasitological protocol. The subjects were also screened for clinical manifestations of lymphatic filariasis.ResultsOf the 785 persons examined, 48 (6.1%) were positive for microfilariae in their thick blood smear. There was a significant difference in the prevalence of lymphatic filariasis among the various age groups (P < 0.01) although peak prevalence occurred between 41 – 60 years. There was no significant difference in prevalence and density with respect to sex (P > 0.05). The overall mean microfilarial density of the infected individuals was 5.6mf/50 μl. There was a significant variation (P < 0.01) in mean microfilarial density within the communities, ranging from 4.7 to 6.4 mf/50 μl. The only clinical sign found in the study area was lymphoedema of the leg recording 2 (0.3%) prevalence.ConclusionsThe National Lymphatic Filariasis Elimination Programme should intervene by expanding the distribution of albendazole and ivermectin to all endemic areas including Yakurr Local Government Area of Cross River State, Nigeria.

Monitoring of tobramycin levels in patients with cystic fibrosis by finger-prick sampling: Figure 1–

To the Editors: Chronic pulmonary infection is the major cause of morbidity and premature mortality in patients with cystic fibrosis (CF). The major pathogen for patients with CF is Pseudomonas aeruginosa . Tobramycin, an aminoglycoside antibiotic, is widely used against Gram-negative bacterial infections and is particularly useful for the treatment of P. aeruginosa in patients with CF [1]. Intravenous tobramycin has a narrow therapeutic range and monitoring of the drug is required to reduce serious side-effects, such as nephrotoxicity and ototoxicity [2]. Dosage alterations based on the results of drug monitoring can improve efficacy and minimise toxicity. Monitoring currently requires venesection and patients may find finger-prick samples less painful and more acceptable. Finger-prick blood sampling is routinely performed by patients with diabetes mellitus, is an easy technique to teach and uses inexpensive equipment which is widely available. We have previously shown that finger-prick sampling is a safe and accurate alternative to venous sampling for measurement of tacrolimus levels in children with kidney transplants [3]. Anecdotal experience in children's hospitals suggest that children generally prefer finger-prick sampling to venous sampling, even where topical anaesthetic agents are used for the latter. Studies in adult patients, including solid organ transplant recipients [4] and those receiving anticoagulant therapy [5], have shown a preference for finger-prick over venous blood sampling. We performed a prospective study to compare the results of tobramycin levels in adult patients with CF measured by finger-prick samples with those from …

Evaluation of the New OneTouch Verio Versus FreeStyle Lite Glucose Meter and the Beckman DxC800 Laboratory Analyzer

Background Johnson & Johnson released the OneTouch Verio strip in September 2010. Here we compare the performance of this new meter with the modified Abbott FreeStyle Lite meter using capillary, venous lithium heparin whole blood, venous lithium heparin plasma, and serum in accordance with International Standards Organization 15197 criteria. Methods The evaluation included imprecision, patient comparison, and interference studies. Both healthy and diabetic participants were recruited, and the results of the 2 meters were compared with the Beckman DxC800 glucose method. The interferences tested included galactose, maltose, lactose, Icodextrin, Intragam, paracetamol, ascorbic acid, hematocrit, hemolysis, lipemia, and variable storage temperature. Results The imprecision at all levels for the 2 meters was less than 5%. With the finger prick capillary samples, there was 80% and 83% compliance with the International Standards Organization guideline not the 95% or greater recommended, with a mean difference of 0.6 and −0.4 mM by the OneTouch Verio and FreeStyle Lite meters, respectively. Ascorbic acid was the only interference common to both meters. The OneTouch Verio suppresses and reports an error with affected results, but the FreeStyle Lite reports a falsely elevated result without warnings. Hematocrit at very high levels produced low results with the FreeStyle Lite strip only. Conclusions The OneTouch Verio analytically performed well. Owing to the differences between the 2 meters, it is best that the 2 meters not be used interchangeably. One type of meter should be consistently used to ensure accurate monitoring. The interference studies showed that, apart from slight differences with ascorbic acid and hematocrit, the 2 meters were unaffected by any of the compounds tested.

Next-generation, fast and accurate point-of-care test for NT-proBNP based on Magnotech technology

In the emergency care setting, where time is of the essence, there is a need for fast and reliable information on NT-proBNP levels for diagnosis and management of acute dyspnea. Rapid NT-proBNP testing near the patient has the potential to streamline the process of care, but only if it is robust, fast and accurate enough to operate safely at the point of care (POC). Here we report on a novel NT-proBNP POC test which can be entirely carried out in a handheld device. This test has the potential to be rapid (<8 minutes), easy to use (fingerprick sampling), and with good accuracy compared to state-of-the-art automated laboratory assays.

Utility of the point of care CD4 analyzer, PIMA, to enumerate CD4 counts in the field settings in India

BackgroundIn resource limited settings non-availability of CD4 count facility at the site could adversely affect the ART roll out programme. Point of care CD4 enumerating equipments can make the CD4 count available at the site of care and improve the patients’ management considerably. This study is aimed at determining the utility of a Point of Care PIMA CD4 analyzer (Alere, Germany) in the field settings in India.MethodThe blood samples were collected from 1790 participants at 21 ART centers from different parts of the country and tested using PIMA and the reference methods (FACSCalibur, FACSCount and CyFlow SL3). The paired finger prick and venous blood samples from 175 participants were tested by the PIMA CD4 Analyzer and then by FACSCalibur.ResultThe CD4 counts obtained by PIMA CD4 analyzer showed excellent correlation with the counts obtained by the reference methods; for venous blood the Pearson’s r was 0.921, p < 0.001 and the relative bias was 0.2% (range: -42 to 42%) and for finger prick samples, the Pearson’s r was 0.856 and the relative bias was −9.1% (range: -46% to 27%). For CD4 ranges; <250, 251–350, 351–500 and >500 cells/mm3, the differences in the median CD4 counts obtained by the reference method and the PIMA analyzer were not significant (P > 0.05) and the relative bias were low (−7 to 5.1%). The Intermachine comparison showed variation within the acceptable limit of%CV of 10%.ConclusionIn the field settings, the POC PIMA CD4 analyzer gave CD4 counts comparable to the reference methods for all CD4 ranges. The POC equipment could identify the patients eligible for ART in 91% cases. Adequate training is necessary for finger prick sample collection for optimum results. Decentralization of CD4 testing by making the CD4 counts available at primary health centers, especially in remote areas with minimum or no infrastructure would reduce the missed visits and improve adherence of the patients.

The challenges of managing donor haemoglobin

Haemoglobin screening has long provided blood services with a means to determine the eligibility of prospective donors. Screening aims to protect donors from donating whilst anaemic, minimise the risk of anaemia developing as a result of donation and ensure an adequate red cell component for the transfusion recipient.Addressing the limitations, risks and benefits of haemoglobin screening to both donor and recipients requires continuous surveillance and an evidence‐based response to evolving clinical research and technological innovations. Challenges include determination of appropriate thresholds in specific populations, management of donors with low haemoglobin, realising the limitations of haemoglobin as a predictor of iron status, and the assessment and selection of alternative screening devices.Current haemoglobin thresholds are now in doubt, with recent large US population studies re‐defining normal ranges for haemoglobin. A further confounding factor is local and international research highlighting the significant prevalence of iron deficiency in eligible donor populations. This reinforces the limitations of haemoglobin as a stand‐alone point of care screening test.Current practice at the Australian Red Cross Blood Service (Blood Service) to assess donor haemoglobin involves a pre‐donation capillary finger prick sample analysed on the HemoCue® 201+. Minimum thresholds for whole blood donation are 120 and 130 g/l for females and males respectively. Donors with low haemoglobin are deferred, offered ferritin testing, and referred to their GP for management if subsequently identified as anaemic and/or iron deficient.The management of low haemoglobin deferrals is currently under review. These account for 16% of all deferrals. Routine ferritin testing of low haemoglobin‐related deferrals indicates 75% are associated with iron deficiency, with approximately 60% in females aged ≤50 years. Local research indicates a substantial loss of donations due to delayed or non‐return following a low haemoglobin deferral. Additional local research suggests that screening with haemoglobin and iron indices enables prediction of donors at risk of subsequent anaemia and who would most benefit from prevention strategies.Technological advances may allow additional means by which to improve donor experience and safety. These include the use of a more palatable non‐invasive haemoglobin analyser, and point of care ferritin testing, both of which are to be assessed by the Blood Service for accuracy and feasibility of implementation.The greatest challenge is to manage the balance of donor health and well‐being with the potential supply loss from healthy donors. To optimise donor iron status and subsequently improve efficiency and supply through reduced deferrals and improved return rates, the Blood Service is considering a comprehensive targeted strategy. Options include improving informed decision‐making for donors, education, ferritin screening, donation frequency modification and/or iron supplementation. Our recently completed randomised, double blind trial of carbonyl iron supplementation in premenopausal female blood donors will be a valuable resource in the development of this strategy. Initiatives need to be responsive to the needs and expectations of donors, community and health professionals, whilst considering the immediate and long‐term impacts on inventory and logistics of implementation. The Blood Service has established a cross‐functional Iron Taskforce to scope and develop such strategies.

Screening for the sickle cell gene in Chhattisgarh state, India: an approach to a major public health problem

The aim of this study is to determine the feasibility of large-scale population screening for the sickle cell gene in high risk areas with limited resources. A programme designed to detect the sickle cell trait and sickle cell disease has screened 359,823 subjects among 2,087 (99.7%) of the villages in Raipur District, Chhattisgarh State, India between October 2007 and June 2010. Children aged 3-15years were initially screened in the villages by solubility tests on fingerprick samples. Venipuncture was performed on subjects with positive solubility tests, and the samples were transferred to Raipur Medical College for alkaline haemoglobin electrophoresis. The sickle cell trait occurred in 33,467 (9.30%) and an SS phenotype in 747 (0.21%). The gene frequencies were not in Hardy-Weinberg equilibrium most likely due to a deficiency of the SS phenotype failing to enter the sampled population from either sickness or early death. Subjects with abnormal haemoglobin genotypes may factor this information into decisions regarding marriage and avoid the risks of having children with sickle cell disease. The techniques described may be a model for other developing societies with limited resources.

Introduction of Rapid Tests for Large-Scale Syphilis Screening Among Female, Male, and Transgender Sex Workers in Mumbai, India

Despite widespread availability of rapid plasma reagin (RPR) for syphilis screening at sex worker (SW)-dedicated project clinics, uptake of syphilis testing remains low and prevalence of syphilis remains high among SWs in Maharashtra, India. The primary reasons given for refusal of RPR were fear of venipuncture and long waiting times for results. Between December 2007 and February 2008, rapid point of contact diagnostic tests (Syphicheck-WB, Qualpro Diagnostics, India) using finger-prick samples were introduced for syphilis screening, with RPR confirmation test of positives. Uptake of syphilis screening among clinic attenders increased to 63.1% compared with an average of 14.3% before the intervention. Among the 19,809 SWs who were screened, 598 tested positive (3% prevalence of lifetime infection). Of these, 395 (66.1%) accepted RPR confirmation test; 337 (88.3%) were seroreactive, 160 (40.5%) had titers ≥1:8 (active syphilis). The projected overall prevalence of active syphilis among all SWs screened was 1.2% but varied by site and typology of sex work (brothel-based, 2.4%; bar-based, 0.5%; street-based, 2.3%; male SWs, 0.2%; transgender, 11.3%; home-based, 0.6%). The introduction of rapid tests dramatically increased the uptake of syphilis screening in this large-scale intervention among a high-risk population in India. However, only two-thirds of SWs with a positive rapid test accepted a confirmatory RPR test. The high proportion (40.5%) of active syphilis among those testing positive on the rapid screening test justifies treatment even if confirmatory testing is declined. A commercially available, simple, rapid nontreponemal test is needed to further strengthen syphilis screening.

Blood Parameters Comparison Using the Cholestech LDX® System and a Standard Clinical Laboratory Assay Technique

Measurement of blood lipid profiles and glucose is standard when evaluating chronic disease risk factors. As an alternative to basic blood draws, compact analyzers have been developed which are promoted as a less expensive and invasive way to provide data. PURPOSE: To compare total cholesterol, HDL, LDL, triglycerides, and glucose concentrations between a standard laboratory assay technique and a Cholestech LDX® system. METHODS: After providing informed consent, 23 participants (49.13 ± 7.67 yrs) had their blood tested after fasting for a minimum of 10 hours, once by a Cholestech LDX® System utilizing a finger prick sample, and once by a standard laboratory assay technique using an antecubital venous sample. The two measurements were done approximately one week apart. Comparisons were done between total cholesterol, HDL, LDL, triglycerides, and glucose concentrations using a paired samples t-test. RESULTS: Data is reported as Cholestech LDX® system vs. standard laboratory assay technique. No significant difference was found for total cholesterol (176.5 ± 32.15 vs. 178.20 ± 29.836, p=0.518) and LDL (95.95 ± 32.82 vs. 97.40 ± 29.11, p=0.616). A significant difference between the two instruments was seen in measurements of HDL (56.55 ± 12.87 vs. 60.45 ± 10.81, p=0.005), triglycerides (120.67 ± 41.95 vs. 100.71 ± 30.03, p=0.018), and glucose (83.76 ± 8.85 vs. 93.48 ± 8.65, p<0.001). CONCLUSION: Using the Cholestech LDX® System to evaluate blood parameters should be approached with caution. Data from this study suggest using the Cholestech LDX® System may be appropriate for screening of total cholesterol, but its use appears limited for research purposes or for other parameters beyond total cholesterol.

Accurate CD4 T-cell enumeration and antiretroviral drug toxicity monitoring in primary healthcare clinics using point-of-care testing

To evaluate the accuracy of point-of-care tests (POCTs) for CD4 cell, clinical chemistry and hemoglobin in primary healthcare clinics in Mozambique. POCT and laboratory-based assays were conducted on adult HIV-positive patients enrolled consecutively at primary healthcare clinics in Mozambique. Patients were tested on-site with POCT CD4 (Pima), clinical chemistry (Reflotron) and hemoglobin (HemoCue) devices using finger prick blood. Results obtained on paired blood samples were used for agreement analysis (bias and limits of agreement). Repeatability analysis was also performed for POCT CD4 cell counting. Primary health nurses operating the Pima, Reflotron and HemoCue POCT devices produced results with low levels of bias for CD4(+) T-cell counts (-52.8 cells/μl), alanine aminotransferase (-0.2 U/l), aspartate aminotransferase (-4.0 U/l) and hemoglobin (0.95 g/dl). CD4(+) T-cell counts in paired specimens of finger prick and venous blood tested on the POCT CD4 device were in close agreement (bias -9 cells/μl, coefficient of variation 10.6%). The repeatability of POCT CD4 cell counting was similar to that observed with laboratory instruments (bias -6.2 cells/μl, coefficient of variation 10.7% vs. bias -5.7 cells/μl, coefficient of variation 7.5%). Primary health clinic nurses generated accurate results for CD4(+) T-cell counts, liver enzymes and hemoglobin using simple POC devices on finger prick samples at decentralized antiretroviral therapy (ART) clinics. POC diagnostics to monitor ART at primary healthcare level is technically feasible and should be utilized in efforts to decentralize HIV care and treatment.

Therapeutic drug and biochemical monitoring in a community pharmacy: Part 1

Abstract A therapeutic drug and biochemical monitoring service within the primary health care sector could provide positive patient outcomes. We have evaluated the possibility of measurements being made by a community pharmacist. Simultaneous blood samples were taken from a finger prick and vein of 55 patients attending a hospital outpatient clinic. The plasma drug concentrations (digoxin, carbamazepine, phenytoin and theophylline) and biochemical parameters (creatinine, potassium and urea) of these finger prick and venous samples were measured in a community pharmacy using the Ames Seralyzer and Clinimate systems. Similar measurements of the venous samples were made by the biochemistry department of a local hospital. There was no significant difference between the concentrations of the two samples (finger prick and venous) measured in the community pharmacy or between the community pharmacy measurements and those carried out by the hospital biochemistry department. External and internal quality control by the community pharmacist was satisfactory. Interpretation of the measured drug concentrations showed that optimal dosing was achieved in only 58.3, 33.3, 50.0 and 28.3 per cent of patients prescribed carbamazepine, digoxin, phenytoin and theophylline, respectively. Interpretation of biochemical concentrations showed that 38.9 per cent of the patients monitored were either hypo- or hyper-kalaemic; 80 per cent of the monitored patients taking renally excreted drugs required a change in their drug management. Although the patients in this study were attending a hospital outpatient clinic, the results highlight the potential benefit of a therapeutic drug and biochemical monitoring service within the primary health care sector.

Twenty minutes of passive stretching lowers glucose levels in an at-risk population: an experimental study

Can passive static stretching lower blood glucose in an at-risk population? Randomised, within-participant experimental study. 22 adults (17 males) either at increased risk of Type 2 diabetes or with Type 2 diabetes. The participants reported to the laboratory 2hr after eating a meal, and drank 355ml of fruit juice (∼43g carbohydrate). Thirty minutes later, they underwent either a 40min passive static stretching regimen or a mock passive stretching regimen. Stretching consisted of six lower body and four upper body static passive stretches. For the mock stretches, the same positions were adopted, but no tension was applied to the musculature. Blood glucose levels for both the stretching and mock stretching were analysed from a finger prick sample using a hand-held glucometer. Values were obtained at baseline (0min), during the regimen (20min), and after the regimen (40min) on both study days. Compared to mock stretch, stretching resulted in a significantly greater drop in blood glucose at 20min (mean difference 28mg/dL, 95% CI 13 to 43; or 1.57mmol/L, 95% CI 0.72 to 2.39). This effect was also statistically significant at 40min (mean difference 24mg/dL, 95% CI 9 to 39; or 1.35mmol/L, 95% CI 0.50 to 2.17). These results suggest that passive static stretching of the skeletal muscles may be an alternative to exercise to help lower blood glucose levels.

The Value of Routine Ferritin Measurement In Blood Donors

AbstractAbstract 3353Iron store depletion is a common side effect of whole-blood donation. Iron loss may lead to iron deficiency symptoms such as fatigue, decreased physical and job performance then gradually result in iron deficiency anemia. As of 2004, routine serum ferritin testing was implemented at our Center. We analyzed the impact of this measure on our donor population with regard to hemoglobin level, anemia occurrence and donor deferral due to low hemoglobin. A total of 160'612 intended donations of 23'557 healthy blood donors at a single institution (Blutspendezentrum beider Basel, Basel, Switzerland) between 1996 and 2009 were analyzed. At each visit, complete blood counts were taken from fingerprick samples and donors were deferred if the capillary hemoglobin concentration proved <133 g/L (m) or <123 g/L (f). From 2004 on, serum ferritin was measured systematically. Upon detection of ferritin levels indicative of iron depletion or iron deficiency anemia, donors were contacted by a blood bank physician and received medical counseling. The further procedure of iron supplementation, donation interval extension or GP referral in the case of abnormal history remained at the physician and donor's discretion.Our donor population consisted of 10'893 males and 12'664 females, 8165 being women of childbearing age (age 18–45). Mean hemoglobin concentration of male donors rose from 151.7 g/L (before 2004) to 153.6 g/L after 2004 (difference 1.9 g/L, 95% CI 1.7 – 1.9 g/L). In women of all ages, the mean hemoglobin concentration increased from 135.7 to 138.3 g/L (difference 2.6 g/L, 95% CI 2.4 – 2.7 g/L) (Figure 1). The hemoglobin concentration of women of childbearing age was 134.2 g/L before 2004 and 137.0 g/L thereafter (difference 2.8 g/L, 95% CI 2.6 – 3.0 g/L). To rule out an alternative cause for the increase in hemoglobin, we assessed the evolution of hemoglobin levels in the periods of 1996–2003 and 2004–2009. In the former period, hemoglobin levels decreased at a mean rate of 0.22 g/L (95% CI -0.19 - -0.26 g/L) per year in male donors, whereas no significant change was seen in female donors (mean change 0.04 g/L, 95% CI -0.01 – 0.09 g/L). In the second period (2004 – 2009), mean hemoglobin levels increased in both male (mean increase per year 0.20 g/L, 95% CI 0.14 – 0.25 g/L) and female donors (mean increase per year 0.16 g/L, 95% CI 0.09 – 0.23 g/L). Before the introduction of routine ferritin measuring, 1.6% (95% CI 1.5 – 1.7%) of donors showed anemia according to WHO definitions (m: Hb<130; f: Hb<120). Anemia occurred in 1.1% of our donors after 2004 (95% CI 1.0 – 1.2%, difference before/after 2004 0.5%, 95% CI -0.6 – -0.3%). Frequency of anemia declined in both male donors (before 2004 0.7%, after 2004 0.5%) and in female donors (before 2004 3.6%, after 2004 2.2%). In the group of women of childbearing age, 4.9% (95% CI 4.6 – 5.3%) were anemic before and 3.1% (95% CI 2.7– 3.4%) after 2004 (difference before/after 2004 -1.8%, 95% CI -1.4 – -2.4%). In all visits to our center before 2004, 2.8% of donors (95% CI 2.7 – 2.9%) were not accepted for phlebotomy due to a hemoglobin count below the mandatory threshold. After 2004, the percentage of rejected donors due to a low hemoglobin count decreased to 1.9% (95% CI 1.8 – 2.0%, difference before/after 2004 -0.9%, 95% CI -0.7 – -1.0%). In particular in the group of women in childbearing age a clear reduction of the rejection rates was noted (before 2004: 7.6% CI 7.2 – 8.1%, thereafter: 4.8% CI 4.4 – 5.2%, difference before/after 2004 -2.8%, 95% CI -2.2 – -3.4%). In conclusion, the introduction of systematic serum ferritin measurements allowed an optimized management of donors with iron deficiency, with efficacious prevention of iron deficiency anemia. This resulted in an increase of mean hemoglobin levels in blood donors particularly in women of childbearing age, the population at highest risk for iron deficiency anemia. Both the incidence of pre-donation anemia and the frequency of donors rejected due to low hemoglobin decreased significantly. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Serological markers for Leishmania donovani infection in Nepal: agreement between direct agglutination test and rK39 ELISA

Visceral leishmaniasis (VL) is an important vector-borne disease caused by Leishmania donovani in the Indian subcontinent. The actual incidence and role of asymptomatic infections in the region are not wellknown. We used the direct agglutination test (DAT) and the rK39 ELISA as L. donovani infection markers in 10 VL endemic villages in Nepal. DAT titre distribution showed two subgroups in the population (infected and non-infected individuals), while rK39 did not. The agreement between both tests was moderate (j = 0.53; 95% CI 0.49–0.57). More research is needed to develop validated markers for Leishmania infection.

Detectability of Plasmodium falciparum clones

BackgroundIn areas of high transmission people often harbour multiple clones of Plasmodium falciparum, but even PCR-based diagnostic methods can only detect a fraction (the detectability, q) of all clones present in a host. Accurate measurements of detectability are desirable since it affects estimates of multiplicity of infection, prevalence, and frequency of breakthrough infections in clinical drug trials. Detectability can be estimated by typing repeated samples from the same host but it has been unclear what should be the time interval between the samples and how the data should be analysed.MethodsA longitudinal molecular study was conducted in the Kassena-Nankana district in northern Ghana. From each of the 80 participants, four finger prick samples were collected over a period of 8 days, and tested for presence of different Merozoite Surface Protein (msp) 2 genotypes. Implications for estimating q were derived from these data by comparing the fit of statistical models of serial dependence and over-dispersion.ResultsThe distribution of the frequencies of detection for msp2 genotypes was close to binomial if the time span between consecutive blood samples was at least 7 days. For shorter intervals the probabilities of detection were positively correlated, i.e. the shorter the interval between two blood collections, the more likely the diagnostic results matched for a particular genotype. Estimates of q were rather insensitive to the statistical model fitted.ConclusionsA simple algorithm based on analysing blood samples collected 7 days apart is justified for generating robust estimates of detectability. The finding of positive correlation of detection probabilities for short time intervals argues against imperfect detection being directly linked to the 48-hour periodicity of P. falciparum. The results suggest that the detectability of a given parasite clone changes over time, at an unknown rate, but fast enough to regard blood samples taken one week apart as statistically independent.

Early Infant Diagnosis of HIV Infection in Southeastern Nigeria: Prevalence of HIV Infection Among HIV-Exposed Babies

Vertical transmission of HIV-1 is responsible for a high level of infant mortality necessitating early infant diagnosis. Serologic tests are not useful because of persistence of maternal antibodies in infants. Amplification of the integrated viral genome by PCR is the preferred method of diagnosis of HIV infection in these children. To determine the prevalence of HIV among a cohort of HIV-exposed babies. HIV-exposed infants were recruited for DNA PCR (early infant diagnosis). Babies were enrolled from six weeks of age. Relevant data were collected with the aid of a proforma. Mothers were given pre-test counselling. Heel or finger prick samples of blood on Whatman filter paper were used for DNA PCR testing. Data on the initial 304 babies enrolled for DNA PCR were analyzed. Seven (3.6%) of 192 mother-baby pairs who had received requisite prophylactic anti-retrovirals (PARV) were PCR-positive. In 23 (8.7%) PCR positive babies, their mothers received PARV but the babies had no post exposure prophylaxis (PEP), while two (12.5%) of 16 babies who had received PARV without their mothers turned out PCR-positive. Thirty nine (53.4%) of 73 mother-baby pairs who had no PARV were infected. Exclusive breastfeeding (EBF) rate was 35.5%. In these babies five (18.5%) were infected, while 288 (75%) of babies were exclusive formula fed (EFF), out of which 11 (4.8%) were infected. Forty-seven (15.5%) of the babies were mixed-fed, and 32 (68.0%) of them were infected. Prophylactic ARV in mothers and babies gave a marked reduction in Mother-to-Child-Transmission (MTCT) rate. Feeding BMS conferred a superior protection against (MTCT) than EBF.

Can finger‐prick sampling replace venous sampling to determine the pharmacokinetic profile of oral paracetamol?

WHAT IS ALREADY KNOWN ABOUT THE SUBJECT: Finger-prick blood samples are increasingly used for the clinical and biomedical measurement of drugs and endogenous substance concentration. The use of different sampling sites can give rise to different drug concentration measurements. During the absorption phase, the paracetamol concentration in finger-prick blood samples is significantly greater than that in venous blood samples, following oral administration. Finger-prick and venous blood samples will result in equivalent pharmacokinetic parameters of oral paracetamol only after distribution equilibrium is attained. The drive to increase the availability of paediatric pharmacokinetic data with minimum blood loss has led to the development of micro-sampling techniques. However studies have suggested that pharmacokinetic data from venous or capillary blood samples may not be directly comparable. The aim of this study was to determine whether paracetamol demonstrates concentration differences between finger-prick and venous blood samples. Paired finger-prick and venous blood samples were taken at 0, 15, 30 and 60 min following 1 g oral paracetamol, from 12 male adult subjects. Paracetamol concentration was determined using HPLC and UV detection with a LLOQ of 2200 pg on column. Intra-assay coefficient of variation for paracetamol at the LLOQ was 3%. At 15, 30, and 60 min post dose the median finger-prick paracetamol concentration was 349%, 72%, and 9.3% greater than the equivalent venous concentrations, respectively. Regression analysis confirmed a significant relationship between finger-prick and venous paracetamol concentrations at 15 min (r(2) = 0.81, P = 0.006), at 30 min (r(2) = 0.82, P < 0.0001) and at 60 min (r(2) = 0.87, P < 0.0001) post dose. The regression equation for venous and finger-prick blood concentrations at 15, 30 and 60 min post dose were Venous(15) = Finger(15) - 3.4, Venous(30) = Finger(30) - 3.4 and Venous(60) = 0.68 Finger(60) + 3.06, respectively. Paracetamol demonstrates an arteriovenous difference in concentration, and the use of finger-prick samples may give rise to results which differ from those obtained with traditional venous sampling especially during the first 1 h following drug ingestion.

Assessment of the Nova StatSensor whole blood point-of-care creatinine analyzer for the measurement of kidney function in screening for chronic kidney disease

Point-of-care testing for creatinine using a fingerprick sample and resultant estimated glomerular filtration rate has potential for screening for chronic kidney disease in community settings. This study assessed the applicability of the Nova StatSensor creatinine analyzer for this purpose. Fingerprick samples from 100 patients (63 renal, 37 healthy volunteers; range 46-962 micromol/L) were assayed using two StatSensor analyzers. Lithium heparin venous plasma samples collected simultaneously were assayed in duplicate using the isotope dilution mass spectrometry-aligned Roche Creatinine Plus enzymatic assay on a Hitachi Modular P unit. Method comparison statistics and the ability of the StatSensor to correctly categorise estimated glomerular filtration rate above or below 60 mL/min were calculated pre- and post-alignment with the laboratory method. StatSensor 1 creatinine results (y) were much lower than the laboratory (y=0.75x+10.2, average bias -47.3, 95% limits of agreement -208 to +113 micromol/L). For estimated glomerular filtration rates above or below 60 mL/min, 100% and 87% of results respectively agreed with the laboratory estimated glomerular filtration rate (79% and 96% post-alignment). StatSensor 2 statistics were similar. The 95% limits of agreement between StatSensor creatinine results were -35 to +34 micromol/L. Isotope dilution mass spectrometry alignment of the StatSensor will identify most patients with estimated glomerular filtration rate <60 mL/min, but there will be many falsely low estimated glomerular filtration rate results that require laboratory validation. Creatinine results need improvement.

Pointing out best practice in taking fingerprick samples

The photograph illustrating your reader’s practice profile on hyperglycaemia (learning zone assessment March 10) shows a healthcare professional taking a fingerprick blood glucose sample from a patient’s forefinger.