Within-run CV Research Articles

Assessment of Δ9-THC and Δ9-THCCOOH bias, precision, and ionization suppression/enhancement between solid tissue homogenate and supernatant by LC-MS-MS.

Liquid chromatography-triple quadrupole mass spectrometry (LC-MS-MS) assays are frequently utilized for screening and confirmatory purposes in the forensic toxicology laboratory. While these techniques are excellent for the targeted identification and quantitation of a wide variety of drug classes, validation and determining fit-for-purpose is a significant requirement for each method. In the USA, the American National Standards Institute and Academy Standards Board first edition of Standard 036 currently serves as a primary resource in forensic toxicology method validation and mandates that laboratories evaluate critical performance characteristics to help ensure the production of forensically defensible results. Due to the variability of specimen quality frequently encountered in the discipline of postmortem toxicology, the State of Maryland Office of the Chief Medical Examiner Forensic Toxicology Laboratory routinely analyzes solid tissue specimens as part of the medicolegal death investigation process and evaluates liver as a representative solid tissue matrix during method validation. Authentic postmortem specimens (e.g. liver, kidney, skeletal muscle, and spleen) were used to investigate the effects of analyzing solid tissue homogenate versus solid tissue supernatant on bias, precision, and ionization suppression/enhancement of Δ9-THC and Δ9-THCCOOH. Bias was <20% for Δ9-THC and Δ9-THCCOOH in liver homogenate and supernatant with a single exception of the low QC concentration for Δ9-THC in liver homogenate (-29%). Within-run and between-run CV was <20% for Δ9-THC and Δ9-THCCOOH in liver homogenate and supernatant. Δ9-THC and Δ9-THC-d3 exhibited significant ion suppression in both liver homogenate and supernatant, while Δ9-THCCOOH and Δ9-THCCOOH-d3 showed both ion suppression and enhancement in these matrices. Noticeable quantitative differences were observed in authentic postmortem solid tissue homogenate and supernatant specimens despite evaluating identical tissue samplings. A brief discussion of the results is presented using a validated LC-MS-MS method for the confirmation and quantitation of Δ9-THC and Δ9-THCCOOH in postmortem casework.

Comparison of results of two hematological analyzer systems: Dirui BF-7200 and Sysmex XN-1000

Abstract Objectives Complete blood count (CBC) is performed using automated hematology analyzers. It is important that CBC results are comparable, reproducible, and reliable. In this study, our aim is to compare the results of Sysmex XN-1000 and Dirui BF-7200 hematology analyzers. Methods Patient samples randomly selected from the routine workflow for each instrument were measured 20 consecutive times to assess reproducibility. The mean, standard deviation, and coefficient of variation (CV%) were calculated for each hematological parameter. A comparison of results from the evaluated Dirui BF-7200 system with those from the current hematology analyzer Sysmex XN-1000 system was made for all of the samples included in the study. The compatibility between the parameters was evaluated using Passing–Bablok and Bland–Altman analyses. Results The within-run CV% values were outside the desirable biological variation database (European Federation of Clinical Chemistry and Laboratory Medicine) specification for CV% for eosinophil, basophil, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean platelet volume and platelet distribution width expressed as standard deviation in the Sysmex XN-1000 instrument and eosinophil, basophil, hematocrit and indexes of red blood cell and platelet in the Dirui BF-7200 instrument. When the Bland–Altman and Passing–Bablok analysis results were evaluated together, most parameters showed poor agreement; only white blood cells and lymphocytes showed good agreement between the two instruments. Conclusions As there is variability between results from different hematology analyzers, we recommend analyzing patient samples in the same laboratory using the same analyzer to avoid different results that could be misinterpreted.

Usefulness of lysophosphatidylcholine measurement in the cerebrospinal fluid for differential diagnosis of neuropathic pain: Possible introduction into clinical laboratory testing

BackgroundThe differential diagnosis of neuropathic pain, especially discrimination between neuropathic pain caused by spinal canal stenosis (SCS) and neuropathic pain associated with causes other than SCS, is sometimes difficult; however, it is important for surgical application. MethodsWe established a reliable method for measuring lysophosphatidylcholine (LPC), a precursor of lysophosphatidic acids which are known as being pain initiators, using a liquid chromatography-tandem mass spectrometry method, and measured the LPC concentrations in the cerebrospinal fluid (CSF) in patients with SCS (SCS group; n = 76), patients with neuropathic pain caused by non-SCS diseases (Others group; n = 49), and control subjects without pain (control group; n = 92). ResultsBoth within-run and between-run CV(%) were almost < 10 %, suggesting an enough performance for clinical introduction. The CSF concentrations of LPC (16:0) and LPC (18:0) were higher in the SCS group than those in the Control or Others group; the concentrations of LPC (18:1), LPC (18:2), LPC (20:4), LPC (22:6) levels were higher in the SCS group than those in the control or others group, but they were also higher in the Others group than those in the control group. The areas under the curve in the ROC curve analyses of LPC (18:1) for discriminating between the SCS and control groups, others and control groups, and SCS and others groups were 0.994, 0.860, and 0.869, respectively. ConclusionsLPC measurement in the CSF is useful for the differential diagnosis of neuropathic pain, especially for surgical decision-making, which is expected for clinical introduction.

Validation of Neutrophil gelatinase associated lipocalin (NGAL), a urinary biomarker for Acute Kidney Injury and the positive interference from high leukocyturia samples

Abstract Acute kidney injury (AKI) is a sudden and serious kidney damage condition that affects more than 1.2 million people every year. KIDNEY DISEASE IMPROVING GLOBAL OUTCOMES (KDIGO) guidelines currently suggest measuring the increase of serum creatinine as a diagnostic marker for AKI. However, the elevation of serum creatinine levels can take up to seven days or when &amp;gt;50% kidney function is lost. Neutrophil gelatinase-associated lipocalin (NGAL) has been identified as an early biomarker for tubular injury, which can be detected in the urine of AKI patients in as early as three hours. In the current study, we evaluated the performance of BioPorto’s (Hellerup, Denmark) NGAL assay, which uses particle enhanced turbidimetry immunoassay (PETIA) technology on the Roche (Indianapolis, USA) cobas c502 chemistry analyzer. Linearity was determined using linearity material from BioPorto and also verified by serial dilutions of a high NGAL patient sample. The limit of quantitation was determined by running urine samples with values of 20 ng/mL, 25 ng/mL, and 35 ng/mL, respectively in duplicate for 10 days. Within-run precisions were determined by running urine two samples containing 100 ng/mL and 400 ng/mL NGAL 20 times and between–run precisions were determined by running the same samples 2 times a day for 10 days. To determine the accuracy of the NGAL method on cobas 502, 40 samples were used to compare results with those measured on Siemens Atellica using the BioPorto’s NGAL assay. Reference interval was verified in 40 urine samples collected from healthy donors. A urine dipstick test was performed to confirm the normal urine samples did not contain leukocyte esterase activity. Since NGAL is also present in neutrophils, we evaluated the effect of leukocytes in urine with the NGAL assay. Results showed the sample with 75 leukocytes/µL had an NGAL of 68 ng/mL and the sample with 500 leukocytes/µL has an NGAL of 222 ng/mL. The linearity range was determined to be 0 - 3000 ng/mL with a limit of quantification of 26 ng/mL. The within-run precision mean and CV% are 121 ng/mL, 4.3% for Level 1 and 401 ng/mL, 1.8% for Level 2. Between-run precisions mean and CV% are 106 ng/mL, 4.8% for Level 1 and 399 ng/mL, 2.6% Level 2. Method comparison had a slope of 0.90 and an intercept of 32.9. The reference interval was determined to be &amp;lt;50 ng/mL and Leukocytes in urine did cause false-positive NGAL results.

CFTR protein quantification as a cystic fibrosis diagnostic biomarker in dried blood spots using multiple reaction monitoring tandem mass spectrometry

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel found on the apical surface of epithelial cells in the airway and gastrointestinal tract. A mutation in the CFTR protein is responsible for developing cystic fibrosis (CF) disease. Therefore, circulating CFTR protein could be a promising biomarker of CF disease.Multiple methodological challenges are associated with CF's available diagnostic and screening methods, such as low specificity and potential false discovery rate, mainly for ethnic groups whose CFTR mutations are not covered in the mutation panels.Herein, we have developed an absolute quantification (AQUA) method based on two CFTR signature peptides (SPs). A liquid chromatography-tandem spectrometry (LC-MS/MS) method in multiple reaction monitoring (MRM) mode (MRM transitions 1168.90 > 85.929 and 707.19 > 85.93 of SP1 and SP2, respectively) enabled the accurate quantification of CFTR protein in a dried blood spot (DBS). The method was validated successfully based on international guidelines in terms of signal linearity, precision (within-run CV 3.37–8.54%; between-run CV 5.15–11.06% for the selected SPs), and accuracy (within-run 93.4–105.59%; between-run 97.45–103.28% for the selected SPs). The level of soluble CFTR protein was evaluated as a potential biomarker for CF using patients (n = 39) and healthy controls (n = 30), were found to be in CF patients lower than controls. For instant, the level of signature peptide 1 (SP1) was 2.09 ± 0.55 nM, 68.77 ± 1.40 nM in CF patients compared to Ctrl, respectively; p < 0.0001.This study is the first to report CFTR levels in DBS using signature peptides by LC-MS/MS as a diagnostic marker for CF. The receiver operating characteristic (ROC) for CFTR SP1 and SP2 showed a significant area under the curves (AUC) 0.7714 (99% CI, p < 0.0001), and 0.8234 (99% CI, p < 0.0001), respectively. The presented MRM method provides a highly specific and sensitive approach to CFTR quantification in a DBS and could be applied in CF screening.

Evaluation and Validation of the Roche Elecsys SARS-CoV-2 Antigen Electro-Chemiluminescent Immunoassay in a Southeast Asian Region.

Introduction: SARS-CoV-2 antigen tests can complement and substitute for RT-PCR tests. Centralized laboratory automated SARS-CoV-2 antigen tests that can be scaled to process a large number COVID-19 cases simultaneously are now available. We have evaluated the new Roche Elecsys SARS-CoV-2 antigen electro-chemiluminescent immunoassay. Methods: The Roche SARS-CoV-2 antigen assay is a double-antibody sandwich electro-chemiluminescent immunoassay, which reports a cut-off index (COI) (COI ≥ 1.0 considered positive). We assessed assay precision and linearity, and confirmed the reactivity limit. We determined the assay sensitivity and specificity with a verification group (289 controls and 61 RT-PCR positive COVID-19 cases). Assay performance was also validated against the consecutive samples we received (7657 controls and 17 cases) for SARS-CoV-2 antigen testing from June to October 2021. Result: The assay had a within-run precision CV of 3.0% at COI 0.68, and a CV of 1.5% at COI 3.49. Between-run precision was 3.0% at COI 0.68 and 1.8% at COI 3.49. The assay was linear from COI 0.65 to 7.84. All 35 C50 ± 20% test results performed over 7 days were positive/negative, respectively. In the verification group, overall sensitivity was 42.6% (26/61 positive, 95% CI 30.0–55.9), and specificity was 99.7% (1/289 positive, 95% CI 98.1–100). The agreement between the SARS-CoV-2 antigen and the RT-PCR cycle threshold (Ct) count was good (r = 0.90). In cases with Ct counts ≤ 30, the antigen assay sensitivity improved to 94.7% (18/19 positive, 95% CI 74.0–99.9). In our validation group, antigen sensitivity was 62.5% (5/8 antigen positive, 95% CI 24.5–91.5) within the first week of disease onset, but no cases were reactive after the first week of disease onset. Conclusion: The Elecsys SARS-CoV-2 antigen assay has good performance within manufacturer specifications. The sensitivity of the Roche antigen assay was greatest when used in patients with lower RT-PCR Ct values (≤30) and within the first week of disease onset.

Volumetric absorptive microsampling as a suitable tool to monitor tyrosine kinase inhibitors

Therapeutic drug monitoring (TDM) of tyrosine kinase inhibitors (TKIs) shows significant potential in guiding personalized anticancer treatment. Dried blood microsampling could be a valuable alternative for traditional plasma sampling to provide TDM results faster and to reach a wider audience. Sample collection is easy and patient friendly as only a small volume of blood is collected via a fingerprick. This enables the possibility of home sampling by the patients themselves. Therefore, an LC-MS/MS method was developed and validated for the quantification of bosutinib, dasatinib, gilteritinib, ibrutinib, imatinib, midostaurin, nilotinib and ponatinib in dried blood samples collected via volumetric absorptive microsampling (VAMS). A VAMS device collects a fixed volume of blood (± 10 µL), irrespective of the sample’s hematocrit (Hct). During method validation, special attention was paid to the possible impact of Hct (range 0.18–0.55) on matrix effect (ME), robustness of the extraction, and accuracy of the method.The method was successfully validated based on international guidelines in terms of calibration curves, precision (within-run CV 2.20–14.8%; between-run CV 2.40–12.3%), accuracy (within-run bias 0.34–12.5%; between-run bias −0.15 to 16.2%), carry-over and selectivity. IS-compensated ME and recovery were Hct independent and no significant impact of Hct on the accuracy of the TKI quantifications was observed. All TKIs were stable in VAMS samples stored at −20 °C, 4 °C and room temperature for at least 4 weeks and for 2 days at 60 °C (except ibrutinib). Lastly, we demonstrated a good agreement between liquid blood obtained from patients on TKI treatment and VAMS samples prepared from that venous blood. As this implies that there is no methodological impact of liquid versus dried blood analysis, the presented method can be applied in clinical follow-up studies for determining TKIs in (capillary) VAMS samples with varying Hct levels.

Quantification of eight hematological tyrosine kinase inhibitors in both plasma and whole blood by a validated LC-MS/MS method

Therapeutic drug monitoring (TDM) of tyrosine kinase inhibitors (TKIs) in cancer therapy offers the potential to improve treatment efficacy while minimizing toxicity. Therefore, a high-throughput, sensitive LC-MS/MS method was developed and validated, to be used for personalized treatment of hematologic malignancies. The assay allows the simultaneous quantification in plasma (EDTA and heparin) and whole blood of eight TKIs, including bosutinib, dasatinib, gilteritinib, ibrutinib, imatinib, midostaurin, nilotinib and ponatinib, which are used in the treatment of chronic and acute myeloid leukemia (CML, AML) and chronic lymphocytic leukemia (CLL). The procedure involves simple protein precipitation of 50 μL of sample, a 4-min chromatographic separation by applying gradient elution on a standard reverse phase column, and tandem mass spectrometric detection. The method was successfully validated based on international guidelines in terms of calibration curves, precision (within-run CV 0.74–16.4%; between-run CV 1.65–17.8%), accuracy (within-run bias 0.07–19.8%; between-run bias 0.05 to −17.6%), carry-over (max 19.4%, for ponatinib), selectivity, matrix-effects, recovery (ranging from 61 to 128%), stability (only issues observed for ibrutinib) and dilution integrity. Furthermore, the accuracy of the method was demonstrated by analyzing external quality controls, with a maximum bias of −11.3%. Assay applicability was demonstrated by analyzing authentic plasma and whole blood samples in order to derive blood-plasma ratios and the variation thereof. The latter are important to allow possible blood-plasma conversion when envisaging possible future implementation of TDM via dried blood microsampling. The presented method can be applied in clinical practice for performing TDM of TKIs in plasma and whole blood samples.

Development and Analytical Validation of a Reverse Transcription Droplet Digital PCR (RT-ddPCR) Assay for PD-L1 Transcripts in Circulating Tumor Cells.

PD-L1, an immune checkpoint protein, is an important biomarker for monitoring cancer patients during the administration of cancer immunotherapy. Droplet digital PCR (ddPCR), is a highly sensitive and accurate tool for the quantification of cancer biomarkers in liquid biopsy. We report the development and analytical validation of a novel duplex RT-ddPCR assay for the simultaneous quantification of PD-L1 and hypoxanthine phosphoribosyltransferase (HPRT) (used as reference gene) transcripts in circulating tumor cells (CTCs). RT-ddPCR experimental conditions were first optimized and the assay was analytically validated using synthetic standards and the BB49 and SCC47 cancer cell lines. The developed assay was further applied in 71 peripheral blood (PB) samples from head and neck squamous cell carcinoma (HNSCC) patients and 20 PB samples from healthy donors. PD-L1 and HPRT transcripts were quantified in cDNAs derived from CTCs isolated by a size-dependent microfluidic device. The developed RT-ddPCR assay was directly compared to RT-qPCR using 71 identical patient cDNA samples. Analytical sensitivity was 0.64 copies/μL, while estimation of intra- and interassay variation revealed a high reproducibility (within-run CV%:4.7-23%; between-run CV%:13%). Using the developed RT-ddPCR assay 33/71(46.5%) HNSCC patients' samples were found positive for PD-L1 expression in CTCs, while by using RT-qPCR fewer samples (23/71, 32.4%) were positive (concordance: 55/71, 77.5%). The developed RT-ddPCR assay for PD-L1 in CTCs is highly sensitive, specific, and reproducible; additionally, it offers improved diagnostic sensitivity over RT-qPCR. The clinical utility of the assay should be prospectively evaluated for the real-time monitoring of CTCs of cancer patients under immunotherapy.

Evaluation of Chromogenic Factor VIII Assay Compared with One-Stage Clotting Assay.

Congenital factor VIII (FVIII) deficiency causes hemophilia A due to different types of defects in the FVIII gene. Although the chromogenic measurement is the reference method and shows less variability, a one-stage assay is the most commonly preferred method for measurement of FVIII. In this study, we aimed to evaluate the analytical performances of chromogenic and one-stage assays, and compare the results prior to introduction of newly developed extended half-life recombinant FVIII products. Sixty-six blood samples from residual material of Istanbul Faculty of Medicine, Central Laboratory workflow comprised the study group. Samples were classified; plasma FVIII > 40 IU and FVIII < 40 IU. FVIII activities were measured using one-stage clotting and chromogenic assays on a CS-2500 analyzer. Analytical performances were determined through precision, linearity, carryover, and comparability studies. The within-run CV% of the one-stage assay on the CS-2500 had 1.6%, 2.6%, the between day CV% were 8.5%, 4.9 % for low and high controls, respectively. The within-run CV% of chromogenic method had 1.2% and 0.9%. Both methods demonstrated good linearity (R2 > 0.998), and the comparisons of both assays exhibited good agreement with minor bias for FVIII activity > 40 IU. However, a significant bias was obtained for FVIII activity < 40 IU. We obtained higher results using the one-stage assay compared with the chromogenic assay, and a significant bias was found for the samples lower than 40 IU. The discrepancy can explained by the presence of a weak agreement for samples lower than 10 IU due to the lower detection limit of the chromogenic assay used in this study (1.5%).

A thin-film interferometry-based label-free immunoassay for the detection of daratumumab interference in serum protein electrophoresis

BackgroundDaratumumab (DARA) is a fully human anti-CD38 IgG1-κ monoclonal antibody drug used in the treatment of multiple myeloma (MM). While serum protein electrophoresis (SPEP) is an important assay for diagnosis and monitoring of patients with MM, DARA can appear in the γ-region as a single band and interfere with the interpretation of SPEP results. An approach to detect the interference is measuring the quantity of DARA in serum samples and assessing its impact on SPEP results. Immunoassays based on label-free technologies, i.e. label-free immunoassays (LFIA’s), can achieve real-time immunometric measurement without attaching a reporter molecule (enzyme, fluorophore, etc.) to the immunocomplex. The recorded time course of the immunocomplex formation allows for quantitation on initial binding rate, which facilitates rapid measurement within a few minutes. Based on the thin-film interferometry (TFI) technology, a rapid LFIA was established for the quantitation of DARA in serum samples. MethodsThe TFI-based LFIA for DARA was validated for imprecision (CV), accuracy, limit of quantitation (LOQ), and analytical measurement range (AMR). Interference to the LFIA was evaluated using a group of protein samples, as well as hemolytic, lipemic, and icteric clinical samples. ResultsThe precision of the TFI-based LFIA’s for DARA ranged from 6.5% to 10.7% (within-run CV), and 7.4% to 11.6% (between-run CV), with a bias of −2.1% to 10.1%. The LOQ was 10 μg/ml (n = 4, CV 9.8%), with an AMR ranging from the LOQ to 1000 μg/ml. The LFIA was used to measure 37 patient samples submitted for SPEP testing. The LFIA results were 100% consistent with the history of DARA use as documented in the medical record. ConclusionsThe TFI-based LFIA was successful at accurately identifying DARA in serum samples and can be used to identify DARA interference in SPEP testing. This work demonstrates the applicability of label-free technologies, particularly the TFI technology, to clinical diagnostic needs. Given the simplicity and the speed of the testing process, the TFI technology provides a unique testing approach for the measurement of proteins in clinical samples.

Capillary hemoglobin electrophoresis of healthy and anemic dogs: Quantification, validation, and reference intervals of hemoglobin fractions.

Despite the advances in canine medicine and the rapid gaining of attention of canine models in biomedical field and particularly in hemoglobin genes research, the studies on canine hemoglobin composition are sparse with ambiguous findings. Our aim was: i) to investigate the electrophoretic pattern of canine hemoglobin and the possible effects of age, sex, and anemia using a capillary electrophoresis assay, and ii) to validate this assay and calculate reference intervals (RIs) for canine hemoglobin fractions. Blood samples were collected from 53 healthy and 42 dogs with regenerative and non-regenerative anemias. The Sebia Capillarys 2 flex-piercing was used for hemoglobin analysis and it was validated using canine blood samples. R statistical language was employed for the statistical analyses. A major hemoglobin fraction (named HbA0) and a minor one (named HbA2) were identified in 100% and 47.4% of samples, respectively. The within-run and between-run CV was 0.1% for HbA0, and 9.1% and 11.2% for HbA2, respectively. The extremely narrow range of HbA0 and HbA2 values hampered a linearity study using canine blood samples. The RIs for HbA0 and HbA2 were 98.9–100% and 0–1.1%, respectively. HbA0 and HbA2 values were not significantly correlated with age (P = 0.866) or reticulocyte count (P = 0.731). No differences were observed in the median HbA0 and HbA2 between the two sexes (P = 0.887), and healthy and anemic dogs (P = 0.805). In conclusion, the capillary electrophoresis revealed a major hemoglobin fraction and an inconsistently present minor fraction. No effect of age, sex, anemia, or regenerative status of anemia was detected. The assay used was validated and RIs were generated, so as to be suitable for use in future investigations.

An automated method for measuring lipoprotein lipase and hepatic triglyceride lipase activities in post-heparin plasma

BackgroundLipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) play a central role in triglyceride-rich lipoprotein metabolism by catalyzing the hydrolysis of triglycerides. Quantification of LPL and HTGL activity is useful for diagnosing lipid disorders, but there has been no automated method for measuring these lipase activities. MethodsThe automated kinetic colorimetric method was used for assaying LPL and HTGL activity in the post-heparin plasma using the natural long-chain fatty acid 2-diglyceride as a substrate. LPL activity was determined with apoCII and HTGL activity was determined without apoCII with 2 channel of auto-analyzer. ResultsThe calibration curve for dilution tests of the LPL and HTGL activity assay ranged from 0.0 to 500 U/L. Within-run CV was obtained within a range of 5%. No interference was observed in the testing of specimens containing potentially interfering substances. The measurement range of LPL activity in the post-heparin plasma was 30–153 U/L, while HTGL activity was 135–431 U/L in normal controls. ConclusionsThe L PL and HTGL activity assays are applicable to quantitating the LPL and HTGL activity in the post-heparin plasma. This assay is more convenient and faster than radiochemical assay and highly suitable for the detection of lipid disorders.

Establishment of a time-resolved fluoroimmunoassay in detection of human epidermal growth factor receptor 2

Objective To set up a time-resolved fluoroimmunoassay (TRFIA) method for human epidermal growth factor receptor 2 (HER2) detection and to evaluate its performance. Methods Each well of the 96-microwell plate was coated with monoclonal antibody of HER2(H7) and another monoclonal antibody of HER2(E5) was labeled by Eu3+ . The sensitivity, stability, specificity, measurement range and reference value of this method were tested. The correlation between chemiluminescence (CLIA) method and TRFIA method was analyzed. Results The sensitivity of HER2-TRFIA method was 0.214 ng/ml. The measurement range was 0.214-1 000 ng/ml. The mean within-run CV and mean between-run CV were 3.48% and 4.13%, respectively. HER2-TRFIA method had no cross-reaction with HER1 and its reference range was 0-13.20 ng/ml. The correlation coefficient between TRFIA and CLIA was 0.997. The same batch of reagents were found to be stable for more than 6 months at 4 ℃. Conclusions HER2-TRFIA method has high sensitivity, specificity, stability and wide detecting range. It might be suitable for clinical use. Key words: Receptor, epidermal growth factor; Breast neoplasms; Fluoroimmunoassay

Anti-AChR antibodies detected by ELISA method using an automated system (SkyLAB 752): evaluation of the analytical performance according to the Clinical and Laboratory Standards Institute (CLSI) EP15-A

Antibodies against the acetylcholine receptor (AChRAb) are currently detected in the clinical Laboratory by using the radioimmunoassay which uses receptors extracted from human muscles, identified and quantified by means of labelling with 125I- $\alpha$ -bungarotoxin. For the first time, Hewer et al. developed a new enzyme-linked immunosorbent assay (ELISA) based on the use of purified foetal and adult AchR. The aim of the study was to validate the ELISA test and define a protocol for its implementation on an automatic instrumentation, according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. Two commercial control sera, high positive (C1, 7.5 nmol/L) and low positive (C2, 1.6 nmol/L), provided by the manufacturer were assayed in triplicate, in five independent runs for within-run, between-day and within-laboratory precision. The four calibrators at different concentration level included in the diagnostic kit (E1, 0.5 nmol/L; E2, 1.0 nmol/L; E3, 6.5 nmol/L; E4, 20 nmol/L) were tested in duplicate in five consecutive days for the trueness study. The commercial controls, tested in the course of precision test, at the mean concentration measured of 11.2 nmol/L (control C1) showed a within-run CV value of 7.9% (95% CI, 0.61 to 1.52), a between-day CV of 8.4% (95% CI, 0.00 to 2.98) and a within-laboratory CV of 11.5% (95% CI, 0.92 to 3.12). At the mean concentration measured of 3.2 nmol/L (control C2) showed a within-run CV of 5.6% (95% CI, 0.13 to 0.32), a between-day CV of 1.9% (95% CI, 0.00 to 0.33) and a within-laboratory CV of 6.0% (95% CI, 0.15 to 0.39). The total repeatability, expressed as Standard Deviation (SD) (within laboratory), resulted 1.27 for C1 and 0.19 for C2, more less than the verification value (1.37 and 0.49, respectively) obtained on the basis of the repeatability declared by the manufacturer [SD (C1) = 0.95874 and SD (C2) = 0.3589]. The analytical performance obtained in “routine activities” has confirmed the specifications produced in the experimental stage and has shown that the reliability of the test persists even when the assay is performed in automation. The good precision and accuracy of the test and its availability on an automated system featuring ease of use and rapid response lead us to conclude that the test is satisfactory for routine use and it is potentially suitable for the long-term monitoring of AChRAb.

Sensitive albuminuria analysis using dye-binding based test strips

BackgroundPopulations at increased risk for chronic kidney disease should be screened for albuminuria. Possibilities of advanced urine strip readers based on complementary metal oxide semiconductor (CMOS) sensor technology were investigated for obtaining quantitative albuminuria results. MethodsReflectance data of test strips (Sysmex UFC 3500 reader+CMOS) were compared with albuminuria (BNII) and with proteinuria (Cobas 8000). Urinary creatinine was assayed using a Jaffe-based creatinine assay (Cobas 8000). ResultsCalibration curve was made between 11.5 and 121.5mg/L with detection limit of 5.5mg/L. Within-run CV values of reflectance data were 0.21% (UC-Control L; 10mg/L) and 0.37% (UC-Control H; >150mg/L) for albumin, and 0.71%/3.97% for creatinine. Between-run CV values were 0.24%/0.42% for albumin and 0.93%/5.13% for creatinine. A strong correlation (r=0.92) was obtained between albuminuria (BNII) and protein strip reflectance data. Creatinine reflectance data correlated well with Jaffe-based urinary creatinine data (r=0.90). Albumin:creatinine ratio obtained by test strip and by wet chemistry showed a good correlation (r=0.59). Carbamylated, glycated and partially hydrolyzed isoforms of albumin could be detected by test strip. ConclusionsDye-binding based albumin test strip assay in combination with a CMOS based reader would potentially allow quantitative analysis of albuminuria and determination of albumin:creatinine ratio.

A sensitive three monoclonal antibodies based automatic latex particle-enhanced turbidimetric immunoassay for Golgi protein 73 detection

Golgi protein 73 (GP73) is a novel and potential marker for diagnosing hepatocellular carcinoma (HCC) that has been found to be abnormally elevated in liver disease. A latex particle-enhanced turbidimetric immunoassay (LTIA) was recently introduced and licensed for application in a variety of automated clinical chemistry analyzers. However, no studies have reported sufficient data on analytical performance of this method when using 3 monoclonal antibodies for GP73 measurement. The experimental conditions were firstly optimized and range of linearity, diagnostic potential, clinical relevance were compared with the LTIA based on polyclonal antibodies and ELISA. Dilution tests for the LTIA using 3 monoclonal antibodies produced a calibration curve from 10 to 350 ng/mL while the polyclonal antibodies produced the curve from 20 to 320 ng/mL. The detection limit was achieved at 1.82 ng/mL concentration. Within-run CV was obtained in the range of 1.5–2.9% and ROC curves indicated sensitivity and specificity of the LTIA based on 3 monoclonal antibodies were 96.7% and 93.3%, respectively, higher than for the polyclonal antibodies (94.6% and 72.4%) and ELISA (70.0% and 83.3%). Therefore, the LTIA assay based on 3 monoclonal antibodies is thus applicable in quantification of GP73 concentration in automated biochemistry analyzers.

Glycation in human fingernail clippings using ATR-FTIR spectrometry, a new marker for the diagnosis and monitoring of diabetes mellitus

Although HbA1c is a good diagnostic tool for diabetes, the precarity of the health system and the costs limit the use of this biomarker in developing countries. Fingernail clippings contain ±85% of keratins, which are prone to glycation. Nail keratin glycation may reflect the average glycemia over the last months. We explored if attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) can be used as a non-invasive tool for assessing glycation in diabetes. Using ATR-FTIR spectroscopy, glycation and deglycation experiments with fructosamine 3-kinase allowed to identify the spectrum that corresponds with keratin glycation in fingernail clippings. Clippings of 105 healthy subjects and 127 diabetics were subjected to the standardized ATR-FTIR spectroscopy method. In vitro glycation resulted in an increased absorption at 1047cm-1. Following enzymatic deglycation, this peak diminished significantly, proving that the AUC between 970 and 1140cm-1 corresponded with glycated proteins. Within-run CV of the assay was 3%. Storage of nail clippings at 37°C for 2weeks did not significantly change results. In diabetics, glycated nail protein concentrations (median: 1.51μmol/g protein, IQR: 1.37-1.85μmol/g protein) were significantly higher than in the controls (median: 1.19μmol/g protein, IQR: 1.09-1.26μmol/g protein) (p<0.0001). ROC analysis yielded an AUC of 0.92 at a cut-off point of 1.28μmol/g nail (specificity: 82%; sensitivity: 90%). No correlation was observed between the glycated nail protein concentrations and HbA1c. Protein glycation analysis in fingernails with ATR-FTIR spectroscopy could be an alternative affordable technique for diagnosing and monitoring diabetes. As the test does not consume reagents, and the preanalytical phase is extremely robust, the test could be particularly useful in developing countries.

Evaluation of a handheld point-of-care analyser for measurement of creatinine in cats.

Objectives The aim of the study was to evaluate whether a handheld creatinine analyser (StatSensor Xpress; SSXp), available for human patients, can be used to measure creatinine reliably in cats. Methods Analytical performance was evaluated by determining within- and between-run coefficient of variation (CV, %), total error observed (TEobs, %) and sigma metrics. Fifty client-owned cats presenting for investigation of clinical disease had creatinine measured simultaneously, using SSXp (whole blood and plasma) and a reference instrument (Konelab, serum); 48 paired samples were included in the study. Creatinine correlation between methodologies (SSXp vs Konelab) and sample types (SSXpwhole blood vs SSXpplasma) was assessed by Spearman's correlation coefficient and agreement was determined using Bland-Altman difference plots. Each creatinine value was assigned an IRIS stage (1-4); correlation and agreement between Konelab and SSXp IRIS stages were evaluated. Results Within-run CV (4.23-8.85%), between-run CV (8.95-11.72%), TEobs (22.15-34.92%) and sigma metrics (⩽3) did not meet desired analytical requirements. Correlation between sample types was high (SSXpwhole blood vs SSXpplasma; r = 0.89), and between instruments was high (SSXpwhole blood vs Konelabserum; r = 0.85) to very high (SSXpplasma vs Konelabserum; r = 0.91). Konelab and SSXpwhole blood IRIS scores exhibited high correlation ( r = 0.76). Packed cell volume did not significantly affect SSXp determination of creatinine. Bland-Altman difference plots identified a positive bias for the SSXp (7.13 μmol/l SSXpwhole blood; 20.23 μmol/l SSXpplasma) compared with the Konelab. Outliers (1/48 whole blood; 2/48 plasma) occurred exclusively at very high creatinine concentrations. The SSXp failed to identify 2/21 azotaemic cats. Conclusions and relevance Analytical performance of the SSXp in feline patients is not considered acceptable. The SSXp exhibited a high to very high correlation compared with the reference methodology but the two instruments cannot be used interchangeably. Improvements in the SSXp analytical performance are needed before its use can be recommended in feline clinical practice.

In vitro Stability of Heat Shock Protein 27 in Serum and Plasma Under Different Pre-analytical Conditions: Implications for Large-Scale Clinical Studies.

The effects of storage temperatures, repeated freeze-thaw cycles, or delays in separating plasma or serum from blood samples are largely unknown for heat shock protein 27 (HSP27). We evaluated (1) the imprecision of the HSP27 assay used in this study; (2) the in vitro stability of HSP27 in blood samples stored at 4℃ for up to 6 hr with immediate and delayed serum/plasma separation from cells; and (3) the in vitro stability of HSP27 in blood samples stored at -80℃ after repeated freeze-thaw cycles. The ELISA to detect HSP27 in this study showed a within-run CV of <9% and a total CV of <15%. After 4-6 hr of storage at 4℃, HSP27 concentrations remained stable when using serum tubes irrespective of sample handling, but HSP27 concentrations decreased by 25-45% when using EDTA plasma tubes. Compared with baseline HSP27, one freeze-thaw cycle had no effect on serum concentrations. However, plasma concentrations increased by 3.1-fold after one freeze-thaw cycle and by 7.3-fold after five freeze-thaw cycles. In conclusion, serum is an appropriate biological sample type for use in epidemiological and large-scale clinical studies.