Correlation between sodium, potassium, hemoglobin, hematocrit, and glucose values as measured by a laboratory autoanalyzer and a blood gas analyzer.

INTRODUCTION: Blood gas analyzers can be alternatives to laboratory autoanalyzers for obtaining test results in just a few minutes. We aimed to find out whether the results from blood gas analyzers are reliable when compared to results of core laboratory autoanalyzers. MATERIALS AND METHODS: This retrospective, single-centered study examined the electronic records of patients admitted to the emergency department of a tertiary care teaching hospital between May 2014 and December 2017. Excluded from the study were patients under 18 years old, those lacking data, those who had any treatment before the laboratory tests, those whose venous gas results were reported more than 30 minutes after the blood sample was taken and for whom any of the laboratory tests were performed at a different time, and recurrent laboratory results from a single patient. RESULTS: Laboratory results were analyzed from a total of 31,060 patients. The correlation coefficients for sodium, potassium, hemoglobin, hematocrit, and glucose levels measured by a blood gas analyzer and a laboratory autoanalyzer were 0.725, 0.593, 0.982, 0.958, and 0.984, respectively; however, there were no good, acceptable agreement limits for any of the parameters. In addition, these results did not change according to the different pH stages (acidosis, normal pH and alkalosis). CONCLUSION: The two types of measurements showed a moderate correlation for sodium and potassium levels and a strong correlation for glucose, hemoglobin, and hematocrit levels, but none of the levels had acceptable agreement limits. Clinicians should be aware of the limitations of blood gas analyzer results.

Sources of variation analysis and derivation of reference intervals for ALP, LDH, and amylase isozymes using sera from the Asian multicenter study on reference values.

BACKGROUND: Sources of variation (SV) of ALP, LDH, and amylase isozymes were explored. METHODS: We analyzed 3511 sera from well-defined healthy individuals recruited during the 2009 Asian project for derivation of common reference intervals (RIs). Up-to-date electrophoresis auto-analyzer and reagents were employed for high resolution and reproducibility. SVs including sex, age, body mass index (BMI), ABO blood groups, and levels of drinking, smoking, and exercise were analyzed by multiple regression analysis. RIs were determined by parametric methods after refining healthy individuals by use of latent reference values exclusion method. RESULTS: Age-related changes in ALP2-3 were different in females: ALP2, linear increase from 20-64y; ALP3, lowering until 45 y and rising steeply thereafter. ALP2 increased with BMI especially in females. ALP5 was barely detectable except in blood-types O and B. Age-related increases in LDH1-LDH3 were noted in females, whereas BMI-related increases were found only for LDH2-LDH5 in both sexes. Pancreatic amylase showed age-related increase in females and was slightly higher in blood-type O. RIs for absolute and relative activities of each isozyme were derived in consideration of sex and age. CONCLUSIONS: Investigation of these isozymes revealed various age-, BMI-, and blood-type-related changes that are all relevant in clinical interpretation of enzyme test results.

Accuracy and clinical utility of a point-of-care HbA1c testing device.

BACKGROUND: Point-of-care testing (POCT) is widely used to measure blood glucose levels in people with diabetes, although its use in measuring glycated hemoglobin (HbA1c) levels is less common, perhaps due to perceived performance issues and access to the technology. METHODS: Forty blood samples were analyzed in duplicate using Bayer's A1CNow + ® Multi-Test A1C system (A1CNow + ) with 3 different reagent lots; HbA1c levels of the samples spanned the clinically relevant range of 4% to 10%. Corresponding samples were sent to a National Glycohemoglobin Standardization Program (NGSP) secondary reference laboratory (University of Missouri Secondary Reference Laboratory #9), which analyzed the samples with a Tosoh Automated Glycohemoglobin Analyzer HLC-723G8 (Tosoh G8; Tosoh Bioscience, Inc). RESULTS: Glycated hemoglobin levels measured with the A1CNow + aligned with measurements obtained using the laboratory method, with correlation coefficients of 0.985, 0.987, and 0.989 for the 3 lots, respectively. The 95% CIs for the differences between the A1CNow + levels and the mean HbA1c levels were within -0.55% to +0.50% for the 3 reagent lots, which is well within the currently acceptable limits of ±0.75% HbA1c required by the NGSP. Results were further analyzed per the new tighter NGSP performance criteria effective September 1, 2012, requiring that 37 of 40 results be within ±7% (relative bias) of the NGSP reference laboratory measures. All 3 lots met the tighter NGSP criteria. CONCLUSION: The A1CNow + provides accuracy and precision when performing POCT of HbA1c as an aid in diabetes management. Ongoing improvements in this and other HbA1c POCT devices may lead to a greater global acceptance of the role of POCT of HbA1c in diabetes management.

Reference ranges for serum cystatin C measurements in Japanese children by using 4 automated assays.

OBJECTIVE: The data available on reference ranges for cystatin C in children are limited, and there are discrepancies among the available data. The aim of this study was to describe the reference ranges for cystatin C in Japanese children by using 4 automated assays. METHODS: Serum cystatin C levels were measured in 1128 Japanese children aged 3 month to 16 years without kidney disease. We calculated age-, gender-, race- and assay-specific cystatin C ranges. RESULTS: For all 4 assays, the median serum cystatin C levels were raised in term infants compared with older children and decreased by the first 2 years. The median serum cystatin C levels remained constant throughout up to the age of 14 years and decreased in children aged 15-16 years. The median serum cystatin C levels in children aged 12-16 years were slightly higher in males than in females. Assay-specific differences were also observed in the levels of serum cystatin C measured. CONCLUSION: Age-, gender-, race- and assay-specific ranges for serum cystatin C should be used as another tool to assess kidney function in children.

A multicenter study on the precision and accuracy of homogeneous assays for LDL-cholesterol: comparison with a beta-quantification method using fresh serum obtained from non-diseased and diseased subjects.

BACKGROUND: Homogeneous assays for low-density lipoprotein-cholesterol (LDL-C) have good precision and are pretreatment-free procedures. However, their accuracies have been questioned, especially in diseased subjects. In this study, we aimed to verify whether LDL-C levels determined by homogeneous assays [LDL-C (H)] agree with those determined by a beta-quantification method [LDL-C (BQ)] in fresh clinical samples. METHODS: We determined LDL-C levels in 49 non-diseased and 124 diseased subjects whose triglyceride (TG) levels were less than 11.29 mmol/L (1000 mg/dL) using 12 homogeneous assays and a BQ method simultaneously. RESULTS: In total, 30.6% of non-diseased subjects and 46.0% of diseased subjects were in the postprandial state. The maximum inter- and intra-assay CVs were 1.8% and 1.5%, and 8 reagents had a CV of 1.0% or less. The mean bias ranged from -0.5% to 1.8% for non-diseased subjects and from -0.7% to 1.6% for diseased subjects. For non-diseased subjects, all but one reagent achieved the National Cholesterol Education Program (NCEP) total error requirement in more than 90% of samples. However, for diseased subjects, the number of reagents that met this requirement was low. With some reagents, LDL-C (H) was higher than LDL-C (BQ), especially in subjects with hypertriglyceridemia. While for other reagents, the difference between the two methods was not associated with hypertriglyceridemia except for type I (n = 2) and type III hyperlipidemia (n = 1). Postprandial sampling was not the main factor for discordant results. CONCLUSIONS: LDL-C (H) agrees with LDL-C (BQ) in non-diseased subjects, but exhibits positive bias for subjects with hypertriglyceridemia in diseased subjects for some reagents.

A method for optimizing and validating institution-specific flagging criteria for automated cell counters.

CONTEXT: Automated cell counters use alerts (flags) to indicate which differential white blood cell counts can be released directly from the instrument and which samples require labor-intensive slide reviews. The thresholds at which many of these flags are triggered can be adjusted by individual laboratories. Many users, however, use factory-default settings or adjust the thresholds through a process of trial and error. OBJECTIVE: To develop a systematic method, combining statistical analysis and clinical judgment, to optimize the flagging thresholds on automated cell counters. DESIGN: Data from 502 samples flagged by Sysmex XE-2100/5000 (Sysmex, Kobe, Japan) instruments, with at least 1 of 5 user-adjustable, white blood cell count flags, were used to change the flagging thresholds for maximal diagnostic effectiveness by optimizing the Youden index for each flag (the optimization set). The optimized thresholds were then validated with a second set of 378 samples (the validation set). RESULTS: Use of the new thresholds reduced the review rate caused by the 5 flags from 6.5% to 2.9% and improved the positive predictive value of the flagging system for any abnormality from 27% to 37%. CONCLUSIONS: This method can be used to optimize thresholds for flag alerts on automated cell counters of any type and to improve the overall positive predictive value of the flagging system at the expense of a reduction in the negative predictive value. A reduced manual review rate helps to focus resources on differential white blood cell counts that are of clinical significance and may improve turnaround time.

Changes in total CO2 measurement according to reagent cassette rotation in chemistry autoanalyzers.

The quality control (QC) failure rate in the serum total carbon dioxide (TCO(2)) test increases at a higher rate than in other tests over time after calibration. The causes of the increased QC failure rate in the TCO(2) test were examined. Using a TBA200RF analyzer (Toshiba Medical Systems), the TCO(2) of the QC material was measured at 2-hr intervals and was found to decrease by up to 16.5% at 10 hr after calibration. In contrast, using the P-module and D-module analyzers (Roche Diagnostics), the TCO(2) of the QC material did not change significantly during 10 hr after calibration. When the TCO(2) level of the QC material was measured hourly over 5 hr with the TBA200FR analyzer while the reagent bottle was rotated at 0, 80, 120, 160, or 200 rpm, the rate of decline of TCO(2), increased over time after calibration and with increasing reagent cassette rotation. Therefore, in a clinical laboratory using an automated analyzer with a rotating reagent cassette, it is necessary to set a limit to the calibration time interval in order to satisfy the QC goal.

The clinical reliability of automated cerebrospinal fluid cell counts on the Beckman-Coulter LH750 and Iris iQ200.

Although automation has improved the accuracy and precision of blood cell counts and is more rapid and less labor-intensive, cerebrospinal fluid (CSF) samples are still counted manually. We compared the IRIS iQ200 Body Fluids Module (Iris Diagnostics, Chatsworth, CA) and the Beckman-Coulter LH750 (Beckman-Coulter, Brea, CA) with manual counts and evaluated the impact of automation on the laboratory if clinically acceptable performance was to be maintained. Automated counts were compared with manual counts on 313 specimens. Clinical reliability was estimated using the weighted kappa coefficient and the impact of errors discussed in the context of a historic census of 3,653 samples spanning 19 months. Nucleated cell counts had a reliability of 0.73 for the LH750 and 0.84 for the iQ200. However, our results showed unacceptable rates of error at counts less than 200/microL (200 x 106/L) for the LH750 and less than 50/microL (50 x 106/L) for the iQ200, representing 94% and 83% of the census specimens, respectively. If clinical reliability is to be maintained, neither the LH750 nor iQ200 would have a significant impact on improving the efficiency of the laboratory because of the high percentage of low CSF cell counts.

Peripheral blood candidosis infection leading to spurious platelet and white blood cell counts.

We report a patient with thrombocytopenia secondary to disseminated stomach adenocarcinoma and sepsis whose platelet and white blood cells were falsely enumerated by two automated haematology analyzers. The cause of the spurious counts became obvious when numerous yeast forms were observed on the peripheral blood smear. Artefactual automated analyzer results are detailed.

Intermethod differences in results for total PSA, free PSA, and percentage of free PSA.

Serum prostate-specific antigen (PSA) assays differ in calibration and response to different PSA forms. We examined intermethod differences in total PSA (tPSA) and free PSA (fPSA) measurements. We tested 157 samples with tPSA concentrations of 2 to 10 ng/mL (2-10 microg/L) using 6 PSA/fPSA method pairs and 1 tPSA method: ADVIA Centaur (complexed and total; Siemens Diagnostics, Tarrytown, NY), ARCHITECT i 2000(SR) (Abbott Diagnostics, Abbott Park, IL), AxSYM (Abbott Diagnostics), IMMULITE 2000 (Siemens Diagnostics), Modular E170 (Roche Diagnostics, Indianapolis, IN), UniCel DxI 800 (Beckman Coulter, Brea, CA), and VITROS ECi (tPSA only; Ortho-Clinical Diagnostics, Raritan, NJ). Regression analysis was performed for PSA, fPSA, and percentage of fPSA with the ARCHITECT i 2000(SR) comparison method. Differences between test and comparison methods were estimated at 2.5, 4.0, and 10.0 ng/mL (2.5, 4.0, and 10.0 microg/L) for tPSA and 15%, 20%, and 25% for percentage of fPSA. Relative differences were more than 10% at 4.0 ng/mL (4.0 microg/L) tPSA for the Centaur, IMMULITE, ECi, and DxI methods. At 20% fPSA, the relative difference was more than 10% for all methods except the AxSYM. Additional harmonization is needed for tPSA and fPSA methods.

Low serum testosterone assayed by liquid chromatography-tandem mass spectrometry. Comparison with five immunoassay techniques.

BACKGROUND: Low levels of serum testosterone, as typically found in women and children, cannot be measured reliably by immunoassays. Our aim was to develop a sensitive assay to quantitate low serum testosterone concentrations using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results were compared to those obtained with various immunoassay techniques. METHODS: Serum testosterone levels in 70 women and children were measured using LC-MS/MS and compared with two automated, non-isotopic immunoassays, and three manual, isotopic immunoassays. Serum extraction was required only for LC-MS/MS and one of the isotopic methods. RESULTS: Deming regression analysis was used for comparison: the correlation coefficients were between 0.772 and 0.870, and the slopes between 0.972 and 1.365. Using Bland and Altman analysis, all the 5 immunoassays showed a positive mean difference compared with LC-MS/MS: all overestimated the testosterone levels in women and children. CONCLUSION: None of the immunoassays tested proved sufficiently reliable when low testosterone concentrations (< or =3.47 nmol/L) were measured. In contrast to conventional isotopic and non-isotopic immunoassay techniques, LC-MS/MS allows the precise determination of low testosterone levels. It has adequate sensitivity and is not subject to interference from other steroids that were tested.

Comparison of Bayer Advia Centaur immunoassay results obtained on samples collected in four different Becton Dickinson Vacutainer tubes.

BACKGROUND: Medicines and Healthcare products Regulatory Agency's (MHRA's) Medical Device Alert MDA/2004/048 described bias in some endocrine test results obtained on a few immunoassay platforms, particularly the Bayer Advia Centaur instrument, when using blood specimens collected into Becton Dickinson (BD) Vacutainer SSTII Advance tubes. As users of BD tubes and the Advia Centaur instrument, we addressed our concerns about the quality of the results that we had previously reported by undertaking an independent study. METHOD: We compared the results of 15 immunoassays performed on Bayer Advia Centaur using blood specimens collected into four different BD Vacutainer tubes (plain, old and newly released BD SSTII Advance, and BD PSTII). RESULTS: Compared with plain tubes, old SSTII Advance tube results showed no bias for testosterone, CA15-3, follicle-stimulating hormone and folate assays, but gave a positive bias for cortisol and a negative bias for vitamin-B12. Compared with plain tubes, BD PSTII tubes gave no significant bias for thyroid function tests, prolactin, parathyroid hormone, and CA125, but gave a negative bias for steroid assays, and a positive bias for gonadotrophins. The results obtained using new BD SSTII Advance tubes were generally comparable with those on plain tubes. CONCLUSIONS: Only for cortisol did our findings support the bias described by MHRA. Based on our results, apart from vitamin-B12 and possibly cortisol, there may have been no significant influence on clinical decisions as a result of using the old BD SSTII Advance specimen tubes. New BD SSTII Advance tubes and plain tubes give generally comparable results. BD PSTII tubes should not be used for steroid hormone measurements on the Bayer Advia Centaur instrument.

A European interlaboratory testing of three well-known procedures for immunocytochemical detection of epithelial cells in bone marrow. Results from analysis of normal bone marrow.

BACKGROUND: This investigation intended to study the unspecific background to be expected in normal bone marrow (BM), comparing three well recognized protocols for immunocytochemical detection of disseminated carcinoma cells. The interlaboratory variation in screening and evaluation of stained cells was analyzed and different screening methods were compared. METHODS: BM mononuclear cells (BM MNC) from 48 normal BMs were immunostained in parallel by three participating laboratories. The protocols, based on three different anti-cytokeratin antibodies, have all been in common use for detection of disseminated carcinoma cells: the A45-B/B3 protocol (Hamburg), the CK2 protocol (Augsburg) and the AE1AE3 protocol (Oslo). For all protocols, the immunostained cells were visualized by the same alkaline-phosphatase (AP) detection system (APAAP) followed by detection of the cells by manual screening and by two different automated screening systems (ACIS from Chromavision and MDS1 from Applied Imaging). Detected AP-visualized cells were morphologically classified into unambiguous hematopoietic (Uhc) and questionable cells (Qc, potentially interpreted as tumor cells). RESULTS: Seven of 48 BMs (15%) harbored > or = 1 AP-visualized cell(s) among 1 x 10(6) BM MNC, both for the A45-B/B3- and for the AE1AE3 protocol, while for CK2 a higher proportion of BMs (21 BMs; 44%) harbored AP-visualized cells (P < 0.01, McNemar's test). The number of Qc was, for all protocols, 1 log lower than the total number of AP-visualized cells. On average, the frequency of Qc was 0.04, 0.08, and 0.02 per 10(6) BM MNC with A45-B/B3, CK2 and AE1AE3, respectively, and the number of Qc-positive BMs 1, 4, and 1. The MDS1 screening sensitivity was similar to manual screening, while ACIS detected fewer cells (P < 0.001, McNemar's test). CONCLUSIONS: All protocols resulted in AP-visualization of occasional hematopoietic cells. However, morphological classification brings the specificity to a satisfactory high level. Approximately 10% of AP-visualized cells were categorized "questionable". The CK2 protocol turned out less specific than the A45-B/B3 and AE1AE3 protocols.

Comparison of 6 automated assays for total and free prostate-specific antigen with special reference to their reactivity toward the WHO 96/670 reference preparation.

BACKGROUND: Prostate-specific antigen (PSA) assays have historically produced different results. Our aim was to investigate the comparability of assay results of selected commercially available assay methods designed to measure total, free, or complexed PSA (tPSA, fPSA, and cPSA). METHODS: We measured tPSA, fPSA, and cPSA in 70 samples and in the WHO PSA 96/670 reference preparation with 6 assays (Beckman-Coulter Access, Abbott ARCHITECT and AxSYM, Bayer Advia Centaur, DPC IMMULITE 2000, and Roche Modular Analytics E170). We also calculated the fPSA/tPSA ratio. RESULTS: The mean deviations from the expected tPSA and fPSA values for the WHO 96/670 reference preparation were 0.37 (range, 0.01-1.32) and 0.19 (range, 0.05-0.49) microg/L, respectively. When plotted against the expected WHO 96/670 reference preparation value, regression slopes varied from 0.99 to 1.22 and r2 from 0.9996 to 1.000. When total PSA was measured in mixtures of sera with high and low tPSA concentrations, the mean (SD) slope of regression of different assays against an in-house method was 1.04 (0.09). In these specimens, the fPSA/tPSA ratio was 0.11-0.14 with different methods. The tPSA and fPSA values in patient samples measured in different assays and plotted against ARCHITECT gave regression slopes from 0.88 to 0.97. The results of the studied assays for tPSA in serum samples agreed within 15%, from each other, and all results for the WHO 96/670 reference preparation were within 6.8% (confidence interval, 1.7%-15.2%) of the expected value. The results for fPSA were more diverse. CONCLUSIONS: Differences among PSA assays appear to have decreased since introduction of the WHO 96/670 reference preparation, but further efforts are needed to harmonize fPSA assays.

Determination of adiponectin in serum using a latex particle-enhanced turbidimetric immunoassay with an automated analyzer.

BACKGROUND: Adiponectin is an adipose-derived hormone that plays a role in regulating metabolic processes such as fat partitioning and lipid and glucose metabolism. Quantification of adiponectin is useful for obtaining information on metabolic syndrome, but there is no rapid method to measure adiponectin for clinical use. METHODS: We developed a rapid and sensitive latex particle-enhanced turbidimetric immunoassay (LTIA) using a latex bead-immobilized anti-adiponectin polyclonal antibody. The assay was performed on a Hitachi H7170 analyzer and evaluated for validity as a method to quantitate adiponectin, in parallel with the ELISA. RESULTS: Dilution tests using LTIA showed linearity from 0.25 to 30 microg/ml. Within-run CV and total CV were obtained in the range of 0.8-1.9% and 1.1-2.0%, respectively. No interference was observed in the testing of specimens containing potentially interfering substances such as bilirubin, ditaurobilirubin, hemoglobin triglyceride, rheumatoid factor, type IV collagen, fibronectin, and complement factor (C1q). A strong correlation between LTIA and ELISA was confirmed (n=30, r=0.990, y=0.95x+0.39). CONCLUSION: The LTIA assay is applicable to quantitating the serum concentration of adiponectin. This assay is more convenient and faster than ELISA and suitable for clinical routine analysis.

Comparison of ACT point-of-care measurements: repeatability and agreement.

BACKGROUND: Accurate control of heparin anticoagulation is necessary during all stages of cardiopulmonary bypass (CPB). The activated clotting time, first described by Hattersley in 1966, is mostly used for determination of anticoagulation. Either celite or kaolin are used as activators. An ACT value of 480 sec is proposed to be the safe minimum level for anticoagulation during CPB. This study was designed to determine if the activated coagulation time (ACT) values of each analyser separately are repeatable, and to determine whether there exists a significant difference in ACT values measured by three different analysers: the GEM PCL (Instrumentation Laboratory), the Hemochron 801 (International Technidyne Corporation) and the ACT II Automated Coagulation Timer (Medtronic). METHODS: All patients underwent cardiovascular surgical procedures requiring heparinisation (200-300 IU/kg). Blood samples for the measurement of the ACT were taken from all patients before and after heparinisation, during CPB, and after protamine administration. All samples were measured in duplicate with the three different analysers. To compare the activated clotting time data, the method described by Bland and Altman was used. The Pearson correlation coefficient was used to determine whether the differences were related to the average ACTs. p-Values <0.05 were considered statistically significant. RESULTS: The results showed that the three tested ACT analysers met the requirements of repeatability. The mean differences and standard deviations of the ACT values measured with the GEM PCL, the Hemochron 801, and the ACT II analyser were, respectively, -8.78 +/- 37.61, -19.77 +/- 68.82, and -6.23 +/- 39.21, with p-values=0.177, 0.081 and 0.384, respectively. The Pearson correlation coefficients were too low (-0.012, -0.221 and -0.241, respectively) to show any correlation between the differences and the means. The ACT values measured with the Hemochron 801 were not significantly different from the ACT values measured with the ACT II analyser: deltaACT =-34.09 +/- 146.68, with p=0.132. However, the GEM PCL did not agree with the Hemochron 801: deltaACT= -80.2 +/- 143.06, with p=0.001, or the ACT II analyser: deltaACT= -119.13 +/- 138.51, with p<0.001. A rather strong correlation was evident between the differences and the means measured with the GEM PCL compared with the Hemochron 801 (r=0.68) and the ACT II analyser (r=0.76). CONCLUSIONS: All analysers used celite or kaolin as activator. However, it was evident that the ACT measurements depended also on the analyser that had been chosen. A precaution that ACT values could not always be interpreted in the same way seems to be necessary.

Quantification of coagulation factors and inhibitors. Still a special task.

This is a very short review on quantitative coagulation factor assays for the beginner. For systematic training several excellent textbooks in German language are available. Quantitative functional assays of coagulation factors and of physiological inhibitor proteins are based on the principle of parallel-line or slope ratio bioassays. With the modern analyzers the test procedure follows the example of clinical chemistry: a single test plasma dilution read from an actual calibration curve, regular internal and external quality control. If there are unexpected results or a suspicion of haemophilia we recommend to repeat the assay with three different pre-dilutions of the test plasma. The resulting potency estimates should not deviate by more than 10-15% from their average. Otherwise the assay is invalid and requires further investigation (e.g. search for inhibitors). Special problems may complicate diagnostic activities. As an example discrepancies between factor VIII one-stage clotting and chromogenic assays are discussed.