Between-run Coefficients Of Variation Research Articles

Separation and identification of underivatized plasma acylcarnitine isomers using liquid chromatography–tandem mass spectrometry for the differential diagnosis of organic acidemias and fatty acid oxidation defects

A simple HPLC–MS/MS method has been established to separate and identify underivatized acylcarnitine isomers. Human plasma samples were deproteinized and concentrated. Acylcarnitines were separated on a reverse phase column and detected with triple quadrupole linear ion trap mass spectrometry. Deuterium-labeled internal standards were used for quantitation. To identify acylcarnitines without pure standards, information-dependent acquisition linking to enhanced product ion scan mode was used. 112 acylcarnitines, including stereoisomers, were found in samples of patients. Dicarboxylic acylcarnitines, such as methylmalonylcarnitine and glutarylcarnitine, were detected with high sensitivity. Three stereoisomers of (R,S)2-methyl-3-hydroxy butyrylcarnitine were detected in samples of patients with β-ketothiolase deficiency. Validation results revealed excellent precision and accuracy of the method. In general the within- and between-run coefficients of variation (CV%) were less than 15%, and recoveries were in the range of 92.7–117.5%. In addition, the reference intervals of acylcarnitines for children aged 3-day to13-year old were established. Using the new method and reference intervals, we have correctly diagnosed 49 patients with fatty acid oxidation defects or organic acidemias in 176 high-risk patients.

Cortisol and cortisone ratio in urine: LC-MS/MS method validation and preliminary clinical application

The determination of urinary cortisol/cortisone ratio is of clinical utility in cases of Cushing's syndrome, apparent mineralocorticoid excess, and also provides information on 11β-hydroxysteroid dehydrogenase (11β-HSD) type 2 activity. It is therefore of utmost importance to ensure accurate cortisol and cortisone measurement and establish appropriate reference ranges. After the isotopic dilution of urine, sample cleanups were obtained with on-line solid-phase extraction and cortisol and cortisone, separated using a Zorbax Eclipse XDB-C18 HPLC analytical column, were analyzed by tandem mass spectrometry with an electrospray ionization source in positive ion mode operation. The method was linear, with concentrations of up to 625 and 1125 nmol/L and lower limit of quantitation (LLOQ) of 5 and 6 nmol/L, for cortisol and cortisone, respectively. Within-run and between-run coefficients of variation were <5% and 6% for cortisol and 6% and 8% for cortisone, respectively. No ion suppression was observed. The non-parametric reference range for the cortisol/cortisone ratio was 0.14-1.09. A simple and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the measurement of cortisol and cortisone in urine. Our findings indicate that the proposed analytical method is suitable for routine purposes and useful in many pathological conditions.

AB1260 Stable performance characteristics of the NOVA view® system makes digital ANA testing objective, accurate and reproducible

BackgroundNOVA View® is a new, automated digital image analysis system, which can be used for reading and interpreting anti-nuclear antibody (ANA) testing on HEp-2 cells, based on measured Light Intensity...

Multiplex serology of paraneoplastic antineuronal antibodies

Paraneoplastic neurological syndromes (PNS) are devastating neurological disorders secondary to cancer, associated with onconeural autoantibodies. Such antibodies are directed against neuronal antigens aberrantly expressed by the tumor. The detection of onconeural antibodies in a patient is extremely important in diagnosing a neurological syndrome as paraneoplastic (70% is not yet known to have cancer) and in directing the search for the underlying neoplasm. At present six onconeural antibodies are considered ‘well characterized’ and recognize the antigens HuD, CDR62 (Yo), amphiphysin, CRMP-5 (CV2), NOVA-1 (Ri), and Ma2. The gold standard of detection is the characteristic immunohistochemical staining pattern on brain tissue sections combined with confirmation by immunoblotting using recombinant purified proteins. Since all six onconeural antibodies are usually analyzed simultaneously and objective cut-off values for these analyses are warranted, we developed a multiplex assay based on Luminex technology. Reaction of serial dilutions of six onconeural standard sera with microsphere-bound antigens showed lower limits of detection than with Western blotting. Using the six standard sera at a dilution of 1:200, the average within-run coefficient of variation (CV) was 4% (range 1.9–7.3%). The average between-run within-day CV was 5.1% (range 2.9–6.7%) while the average between-day CV was 8.1% (range 2.8–11.6%). The shelf-life of the antigen coupled microspheres was at least two months. The sensitivity of the multiplex assay ranged from 83% (Ri) to 100% (Yo, amphiphysin, CV2) and the specificity from 96% (CV2) to 100% (Ri). In conclusion, Luminex-based multiplex serology is highly reproducible with high sensitivity and specificity for the detection of onconeural antibodies. Conventional immunoblotting for diagnosis of onconeural antibodies in the setting of a routine laboratory may be replaced by this novel, robust technology.

The association between sex hormone-binding globulin and type 2 diabetes in Nigerian men.

BackgroundEpidemiological studies have shown that sex hormone-binding globulin (SHBG) has a role in glucose homeostasis in both men and women. However, a prospective study on Japanese-American subjects concluded that SHBG was not a significant risk factor in either men or women, suggesting ethnic differences. We were not aware of any evaluation of SHBG in subjects of African ancestry.ObjectivesWe investigated the association between SHBG and insulin resistance in type 2 diabetic diabetic men in a hospital in Nigeria.MethodForty-eight male subjects with type 2 diabetes and 20 non-diabetic male subjects were recruited in this cross-sectional hospital-based study by the convenient sampling method. Height and circumferences around the waist and hip were measured to the nearest 0.5 cm and the waist–hip ratio was calculated from this measurement. Weight was measured and body mass index was calculated. Fasting plasma glucose concentration was measured by the glucose oxidase method with a between-run coefficient of variation of 3%. Insulin and SHBG were measured by means of enzyme-linked immunosorbent assay (ELISA).ResultsThere was a statistically-significant difference between test results for the diabetic and non-diabetic patients. The mean SHBG concentration was higher in the non-diabetic group (42.2 nmol/L) than the diabetic group (30.5 nmol/L). A significant inverse association between insulin resistance and SHBG was observed (r = 0.353, p < 0.015).ConclusionThis study supported earlier observations that a significant inverse correlation exists between SHBG and insulin resistance and provides evidence that the relationship may extend to type 2 diabetic men of African ancestry in Nigeria.

Urine iodide determination by ion-pair reversed-phase high performance liquid chromatography and pulsed amperometric detection

A sensitive and specific ion-pair reversed-phase high performance liquid chromatography (HPLC) method for urinary iodine analysis is described. This method is based on pulsed amperometric detection (PAD) using a silver working electrode (HPLC–PAD), which improves peak shape, electrode stability as well as linearity and reproducibility. A two-step extraction process consisting of solid phase extraction (SPE) and liquid–liquid extraction with dichloromethane was added in order to improve sample purification which is essential with the use of PAD. Treated samples were eluted on a C18 column, using a phosphate buffer containing ion-pairing reagent tetrabutylammonium and 5% MeOH. The calibration standard curves were linear up to 500μg/L and within-run and between-run coefficients of variation (CVs) were <6% with the quantification limit fixed at 6μg/L. Accuracy, expressed as recovery, ranged from 94% to 104%. Comparison with the Technicon AutoAnalyzer acid digestion (AA) method resulted in a high correlation (r=0.9916). Due to a low quantification limit and high sample throughput, the proposed technique appears suitable for both epidemiological and clinical follow-up studies.

Evaluation of the Performance of ARKRAY ADAMS HA-8180 HbA1cAnalyzer

This article is available from http://www.labmedonline.org 2012, Laboratory Medicine Online This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Hemoglobin (Hb)-A1c is routinely used for the management of diabetes. In 2010, HbA1c was included into the diagnostic criteria for diabetes by the American Diabetes Association. A newly developed HbA1c analyzer, ARKRAY ADAMS HA-8180 (ARKRAY KDK, Japan) was introduced. In this study, we evaluated the analytical performance of ARKRAY ADAMS HA-8180 HbA1c analyzer and compared it with the previously used Variant II Turbo (Bio-Rad Laboratories, USA), which is a National Glycohemoglobin Standardization Program (NGSP) certified analyzer. Methods: According to Clinical Laboratory and Standards Institute (CLSI) evaluation protocol (EP) 5-A, Lyphochek Diabetes Controls (Bio-Rad Laboratories, USA) are used for precision. Two (low and high) levels of quality control materials were analyzed twice a day for 20 days, after which the mean, total standard deviation (SD) and total coefficient of variation (CV), including the between-run CV and between-day CV were calculated. ARKRAY ADAMS HA-8180 HbA1c analyzer and Variant II Turbo were compared with 150 samples according to CLSI EP9-A2. In addition, the linearity and carry over rate were evaluated. Results: Between-run CVs for low and high level quality control materials were 0.0% and 0.3%, respectively, whereas between-day CVs for low and high level quality control materials were 0.3% and 0.2%, respectively. In the linearity test, the coefficient of determination (R) was 0.99 (range, 3.1-19.3%). Thus, a good correlation was observed between ARKRAY ADAMS HA-8180 HbA1c analyzer and Variant II Turbo (R=0.994). The carry over rate was 0.0%. Conclusions: The ARKRAY ADAMS HA-8180 HbA1c analyzer showed excellent precision, linearity, and carryover rate. It also showed excellent correlation with the NGSP certified Variant II Turbo. In conclusion, the ARKRAY ADAMS HA-8180 HbA1c analyzer is a reliable high-performance liquid chromatography (HPLC) analyzer for HbA1c analysis and could be very useful for the diagnosis, treatment, monitoring, and risk assessment of diabetes.

Comparison of Analytical Performance of Two Single-Step Measurement Devices of B-Type Natriuretic Peptide

Rapid measurement of B-type natriuretic peptide (BNP) plays a practical role in the diagnosis of congestive heart failure. Analytical evaluation of a new small-footprint immunochromatography reader of BNP (Rapidpia®) was performed and compared with the commercially available SHIONOSPOT® Reader as the index. The new BNP assay had a within-run coefficient of variation (CV) of 9.0% and a between-run CV of 2.1%. Correlations between whole blood and plasma samples and those with the index SHIONOSPOT® Reader were y = 0.93x + 0.88, R2 = 0.98 and y = 1.08x - 6.67, R2 = 0.93, respectively. Based on our findings, the two point-of care (POC) assays for BNP, Rapidpia® and SHIONOSPOT® Reader, showed comparable results.

Phytoestrogen biomonitoring: an extractionless LC-MS/MS method for measuring urinary isoflavones and lignans by use of atmospheric pressure photoionization (APPI).

We present here a high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying phytoestrogenic isoflavones (daidzein, equol, genistein, and O-desmethylangolensin) and lignans (enterodiol and enterolactone) in urine without the use of extraction or the preconcentration techniques inherent in existing methods. The development of this concept was made possible by use of atmospheric pressure photoionization (APPI); an ionization technique that we found to improve analyte sensitivity relative to electrospray ionization and atmospheric pressure chemical ionization for this particular group of compounds. The analytical performance of this method was equal to or exceeded that of comparable methods. Between-run coefficients of variation (CVs) across three quality control (QC) pool levels analyzed in duplicate over 20 days were 3.1-5.8% CV; within-run CVs were 2.3-6.0%. Accuracy, as determined by average spike recovery in QC pools, was generally within ±10% of being quantitative (100%). Relative limits of detection were 0.04-0.4 ng/mL urine, with absolute detection limits as low as 0.1 pg. This method was applied to the analysis of >2,500 urine specimens for the 2005-2006 Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (NHANES). The method was capable of quantifying these compounds in 95-100% of study samples. This work is the first ever report of using APPI for the LC-MS/MS determination of these compounds in urine. It is also the first method of its kind to do so without any need for analyte extraction or preconcentration prior to analysis.

Screening for von Willebrand disease: contribution of an automated assay for von Willebrand factor activity

Measuring von Willebrand factor (VWF) activity is essential to the diagnosis of von Willebrand disease (VWD). The VWF activity is usually assessed based on measurement of the ristocetin cofactor (VWF:RCo). However, that test is technically challenging and has high intra- and inter-assay variabilities. The HemosIL VWF activity (VWF:AC) is a fully automated assay, recently proposed as a good alternative to VWF:RCo for VWD diagnosis. This study was undertaken to assess this new method. First, the analytical performance of VWF:AC on an automated coagulo-meter (ACLTop) was determined, and then this new method was compared with VWF:RCo and the platelet function analyzer (PFA100) for 160 patients referred for VWD screening. The VWF:AC achieved acceptable precision with within-run and between-run coefficients of variation ranging from 2.3% to 14.1%, and linearity from 10% to 100%. Despite some marked differences between VWF:AC and VWF:RCo for 10 plasmas tested, their agreement for VWD diagnosis was good. The VWF:AC had sensitivity similar to that of PFA100 (close to 100%), but better specificity (97.7% vs. 66% or 60%, depending on the cartridge used). The good analytical performance, and the sensitivity and specificity of VWF:AC to detect VWF deficiency renders it a suitable method for VWD screening. Our findings support VWF:AC use for the diagnostic work-up of VWD, paying close attention to concomitant clinical signs and bleeding score, as recommended for VWD.

Fast measurement of serum amyloid A in different specimens from swine by using a new one-step time-resolved fluorescent immunoassay

The objective of the present study was to develop a one-step, fast, competitive time-resolved fluorescent immunoassay to determine porcine serum amyloid A (SAA) by using species-specific reagents. The assay consisted of an all-in-one format involving only 55 min of incubation that was adapted and validated for use in 3 different specimens: serum, saliva, and meat juice. The method had overall within- and between-run coefficients of variation under 8% and 12%, respectively, and coefficients of determination higher than 0.93 for linearity under dilution analysis for all specimens. The limits of detection were 0.32 mg/l, 0.28 mg/l, and 1.74 mg/l for serum, saliva, and meat juice measurements, respectively. Upper and lower limits of quantification were determined for each sample type and resulted in wide assay ranges that allowed a precise SAA measurement in all the fluids investigated. Statistically significant differences (P = 0.0004 for serum and P < 0.0001 for the saliva and meat juice samples) in SAA levels were found when healthy (n = 20) and diseased (n = 20) pigs were compared. The obtained results indicate that this fast, sensitive, and robust assay for SAA measurement could be of use to determine health and welfare status in swine by employing alternative samples to serum.

Performance Characteristics of the ARK Diagnostics Gabapentin Immunoassay

Gabapentin is an antiepileptic drug used as adjunct therapy in the treatment of seizures. Absorption is saturable, and drug clearance can be reduced if patients have impaired renal function. Therapeutic drug monitoring can be useful for optimizing the dose in patients with impaired renal function, for evaluating individual patient absorption thresholds, and for monitoring compliance. Although chromatographic techniques have historically been used to support gabapentin monitoring, an immunoassay was recently introduced by ARK Diagnostics, for use with open channel chemistry analyzers. Here, we evaluated the immunoassay on a random access instrument. The ARK gabapentin assay was validated using a Beckman AU400e automated chemistry analyzer. Imprecision was assessed with 5 replicates of 3 concentrations (2.5, 8.0, and 25.0 mg/L), analyzed for 4 days. The analytical measurement range was evaluated with duplicate measurements of a prepared sample (40.0 mg/L) that was serially diluted. Patients' results were compared with the results generated with a previously validated ultra-high performance liquid chromatography coupled to tandem mass spectrometry method (n = 45, range, 1.5-45.6 mg/L). The within-run and between-run coefficients of variation were ≤8.1%. The analytical measurement range was confirmed to be 1.5-40.0 mg/L, as stated by the manufacturer. The Deming regression for the results of 45 patients produced a correlation coefficient of 0.9987, a linear regression slope of 1.01, and an intercept of 0.24 when compared with the ultra-high performance liquid chromatography coupled to tandem mass spectrometry assay. The ARK immunoassay is suitable for the clinical use of monitoring gabapentin in serum or plasma on the Beckman AU400e.

Development of a new duplex real-time polymerase chain reaction assay for hepatitis B viral DNA detection

BackgroundQuantification of hepatitis B virus (HBV) DNA can be used for diagnosing HBV infection and monitoring the effect of antiviral therapy. However, probably because of mismatches between the template and primer/probe, HBV DNA in some HBV infections could not be detected using currently available commercial assays with single primer/probe. By aligning the HBV sequences, we developed a duplex real-time polymerase chain reaction (PCR) assay using two sets of primers/probes and a specific armored DNA as internal control (IC).ResultsThe limit of the duplex real-time PCR assay was 29.5 IU/ml, whereas the specificity was 100%. The within-run precision coefficient of variation (CV) ranged from 1.02% to 2.73%, while the between-run CV ranged from 0.83% to 1.25%. The optimal concentration of armored DNA IC in the HBV DNA duplex real-time PCR assay was 1 000 copies/ml. Data from 69 serum samples with HBV infection showed that the performance of the duplex real-time PCR assay was comparable to that of the COBAS Ampliprep/Cobas Taqman (CAP/CTM) HBV assay and was superior to those of the domestic commercial HBV assays.ConclusionsThe duplex real-time PCR assay is sufficiently sensitive, specific, accurate, reproducible and cost-effective for the detection of HBV DNA. It is suitable for high throughput screening and frequent HBV DNA level monitoring.

Clinical multicenter evaluation of a new FXa‐based Antithrombin assay

The determination of functional Antithrombin is a central part of thrombophilia screening. In this multicenter study, a new FXa-based method (INNOVANCE® Antithrombin) was evaluated on four different analyzers. The INNOVANCE Antithrombin method was evaluated by precision and reference interval studies and by comparing the new method with established methods through parallel measurement of samples from 249 patients and 151 apparently healthy individuals. The INNOVANCE Antithrombin assay demonstrated on all analyzers repeatability coefficients of variation (CVs) ≤ 3.2% and within-device and between-run CVs ≤ 6.9%. The reference intervals of all analyzers are comparable with 2.5th percentiles between 80% and 85% of normal. The INNOVANCE Antithrombin and the FIIa-based Berichrom® AT III (A) methods demonstrated good concordance with correlation coefficients of r = 0.908 or higher. The INNOVANCE Antithrombin method demonstrated furthermore an excellent comparability with the STA® Antithrombin III assay and an acceptable comparability with the Coamatic® LR Antithrombin assay. The patients with congenital deficiency (n = 31) were identified with all assays except for the patients carrying the P41L heparin-binding site mutation, which was only identified with the INNOVANCE Antithrombin and the STA Antithrombin III methods. The INNOVANCE Antithrombin assay has high sensitivity for Antithrombin deficiencies and is reliable, precise and suitable for routine clinical use.

Failure to detect Xenotropic murine leukaemia virus-related virus in Chinese patients with chronic fatigue syndrome

BackgroundRecent controversy has surrounded the question of whether xenotropic murine leukaemia virus-related virus (XMRV) contributes to the pathogenesis of chronic fatigue syndrome (CFS). To investigate the question in a Chinese population, 65 CFS patients and 85 blood donor controls were enrolled and multiplex real-time PCR or reverse transcriptase PCR (RT-PCR) was developed to analyze the XMRV infection status of the study participants. The assay was standardized by constructing plasmid DNAs and armored RNAs as XMRV standards and competitive internal controls (CICs), respectively.ResultsThe sensitivities of the multiplex real-time PCR and RT-PCR assays were 20 copies/reaction and 10 IU/ml, respectively, with 100% specificity. The within-run precision coefficient of variation (CV) ranged from 1.76% to 2.80% and 1.70% to 2.59%, while the between-run CV ranged from 1.07% to 2.56% and 1.06% to 2.74%. XMRV was not detected in the 65 CFS patients and 65 normal individuals out of 85 controls.ConclusionsThis study failed to show XMRV in peripheral blood mononuclear cells (PBMCs) and plasma of Chinese patients with CFS. The absence of XMRV nucleic acids does not support an association between XMRV infection and the development of CFS in Chinese.

Rapid Surface Plasmon Resonance Immunoassay for the Determination of Deoxynivalenol in Wheat, Wheat Products, and Maize-Based Baby Food

A rapid screening assay (9 min/sample) has been developed and validated for the detection of deoxynivalenol in durum wheat, wheat products, and maize-based baby foods using an SPR biosensor. Through a single laboratory validation, the limits of detection (LOD) for wheat, wheat-based breakfast cereal, and maize-based baby food were 57, 9, and 6 μg/kg, respectively. Intra-assay and interassay precisions were calculated for each matrix at the maximum and half-maximum European Union regulatory limits and expressed as the coefficient of variation (CV). All CVs fell below 10% with the exception of the between-run CV for breakfast cereal. Recoveries at the concentrations tested ranged from 92 to 115% for all matrices. Action limits of 161, 348, and 1378 μg/kg were calculated for baby food, wheat-based breakfast cereal, and wheat, respectively, and the linear range of the assay was determined as 250-2000 μg/kg.

Development and evaluation of an antibody ELISA for sarcoptic mange in sheep and a comparison with the skin-scraping method

In this work an indirect ELISA for detecting serum-specific IgG antibodies in sheep was developed using a crude saline extract from Sarcoptes scabiei var. ovis mites and then the repeatability of the ELISA outcomes was estimated. Subsequently, its diagnostic accuracy was evaluated by Receiver Operating Characteristics (ROC) analysis using a sample collected from the entire sheep population of western Castile and Leon region in Spain, and then compared with that of the skin-scraping method. The reference method used was a combination of clinical examination, skin-scraping analysis and epidemiological surveys, but it introduced selection and probably information biases. Furthermore, we attempted to identify biological factors useful to predict the sensitivity or specificity of the ELISA as determined by comparison with the reference method. Additionally, conventional latent-class analysis [Hui, S.L., Walter, S.D., 1980. Estimating the error rates of diagnostic tests. Biometrics 36, 167–171] was also used to estimate accuracy parameters. The between-run coefficient of variation (CV) for a standard serum was 8.8% and the within-run CV 4.3%. No significant deviation between the OD% means and strength positive correlation between the OD% values ( r = 0.98) were found for the results from two different batches of antigen. When compared to the reference method, the Area Under the ROC curve (AUC) for the reference population was 0.967 (95% CI: 0.949–0.985) for the ELISA and 0.915 (95% CI: 0.863–0.968) for the skin-scraping method. By logistic regression analysis, one explanatory biological factor—result to the skin-scraping method—and four explanatory biological factors–Tyroglyphidae individual status, Trichophyton verrucosum individual status, Oestrus ovis status of the flock and presence of adjacent animals with a clinical disease neighbour to S. scabiei infection—were found for diagnostic sensitivity and specificity of the ELISA, respectively, although this depended on the OD% cut-off value used. Latent-class analysis, carried out for the ELISA at 17.8 OD% cut-off value (mean plus 3 SDs of sheep considered negative to anti- S. scabiei antibodies), showed a marked difference between the estimated diagnostic sensitivity of the ELISA (87.6%) and the skin-scraping method (62.8%), but closer diagnostic specificities (95.9% vs. 100%, respectively). These results demonstrate that the developed ELISA is valid for different applications in clinical as well as in epidemiological contexts.

Determination of cerebrospinal fluid cystatin C on Architect ci8200

Background Human cystatin C is a cysteine protease inhibitor produced by all nucleated cells in the body and the protein is present in all body fluids. The concentration in cerebrospinal fluid (CSF) is considerably higher than in plasma. Cystatin C levels seem to influence the development of Alzheimer disease (AD) and low levels in the brain are associated with an increased risk for AD. The aim of this study was to develop a high throughput assay for the quantification of cystatin C in CSF. Methods Antigen excess, imprecision, interference, linearity, recovery, sample stability and reference values were evaluated on Architect ci8200 (Abbott Laboratories, Abbott Park, IL, USA). Results The assay had an antigen-excess limit at 23 mg/L and was linear over the range of 0.84 to 8.33 mg/L. Results > 8.33 mg/L were automatically rerun in a higher dilution. Within-run coefficient of variation (CV) was 1.71, 1.10 and 0.79%, between day CV was 1.71, 0.39 and 1.45%, between-run CV was 0.58, 0.66 and 0.48%, and total CV was 2.49, 1.34 and 1.72% at cystatin C concentrations of 1.39, 3.17 and 6.28 mg/L, respectively. The recovery was 97–102%. No interference at a 7.5% deviation level was observed for 8.5 g/L of hemoglobin or 800 mg/L (1368 μmol/L) of bilirubin. Reference values for cystatin C in cerebrospinal fluid obtained with this method were 2.42–14.33 mg/L.

Neonatal screening for mucopolysaccharidoses by determination of glycosaminoglycans in the eluate of urine‐impregnated paper: preliminary results of an improved DMB‐based procedure

The fact that mucopolysaccharidoses (MPSes) are now treatable, and that the earlier treatment is initiated the better, is an indication for neonatal screening. The most efficient approach seems likely to be a multi-tier procedure in which screening for urinary glycosaminoglycan (GAG) is followed by enzyme determinations in heelprick blood of newborns screening positive. Hitherto the method of choice for the determination of GAG has been the measurement of absorbance by a complex of GAG and 1,9-dimethylmethylene blue (DMB). We evaluated a DMB method in which absorbance by DMB is measured following its addition to the eluate obtained from paper-borne newborn urine samples and is normalized relative to urinary creatinine. Calibration is performed with chondroitin-6-sulfate (Ch-6-S). The limits of detection and quantification of GAG were 1.98 and 5.94 mg/dl, respectively. The within-run coefficients of variation (CVs) of the GAG/creatinine ratio for 25, 31, and 70 mg/dl solutions of Ch-6-S in urine were 21.8, 16.4, and 10.5%, respectively, and the corresponding between-run CVs were 25.0, 13.5, and 10.1%. Recovery from the urine spiked with 31 mg Ch-6-S/dl was 94.8%. Accuracy was also acceptable for all other GAGs except hyaluronic acid. For neonatal screening, the diagnostic threshold was tentatively established as 800 mg GAG/g creatinine, the 95th centile of samples from 903 infants aged 3-28 days, but the value of the GAG/creatinine ratio was negatively correlated with age. Application of the new method to samples from older individuals with and without MPS achieved 100% sensitivity and specificity when used with an age-dependent threshold taken from the literature on the original DMB method. If used in the first tier of a multi-tier screening protocol, the proposed method would allow the detection of abnormal levels of all GAGs except hyaluronic acid.

A rapid and sensitive LC–MS/MS method for quantification of four anthocyanins and its application in a clinical pharmacology study of a bioadhesive black raspberry gel

Cyanidin 3-glucoside (C3GLU), cyanidin 3-rutinoside (C3RUT), cyanidin 3-sambubioside (C3SAM) and cyanidin 3-(2 G-xylosyl) rutinoside (C3XRUT) are the four constituent black raspberry anthocyanins that contribute significantly to the chemopreventive effects of freeze-dried black raspberries (FBR). A highly sensitive and specific LC–MS/MS assay was developed and validated to simultaneously quantify these four FBR anthocyanins in human saliva, plasma and oral tissue homogenates. In saliva, the lower limit of quantification (LLOQ) for these anthocyanins was 1.0 ng/mL. The within-run and between-run coefficients of variations (CVs) at the quality control concentrations (1.0, 5.0, 50 and 500 ng/mL) were all <12%, except for C3SAM and C3RUT at the LLOQ, which showed a within-run CV of 18.3% and between-run CV of 16.0%, respectively. The accuracy values ranged from 87.5 to 110%. In plasma, the LLOQ for C3GLU and C3RUT was 1.0 ng/mL and for C3SAM 5.0 ng/mL. The CVs at the above concentrations were <15%, except for C3GLU at the LLOQ, which showed the between-run CV of 16.9%. The accuracy values ranged from 90.7% to 112.7% except for C3GLU at the LLOQ, which showed 119.3%. In tissue homogenates, the LLOQ for C3GLU and C3RUT was 2.0 ng/mL, and C3SAM 5.0 ng/mL. The CVs and accuracy values at concentrations (2.0, 5.0, 50 and 500 ng/mL) were similar to those in human plasma. This assay was subsequently used in a pilot pharmacology study to evaluate the effects of topical application of a 10% (w/w) FBR bioadhesive gel to selected mucosal sites in the posterior mandibular gingiva. Measurable saliva and tissue levels of the FBR anthocyanins confirmed that gel-delivered anthocyanins are readily distributed to saliva and easily penetrate human oral mucosa.