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.

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.

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.

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.

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 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.

Validation of high-throughput methods for measuring blood urea nitrogen and urinary albumin concentrations in mice.

Chronic kidney disease is a substantial medical and economic burden. Animal models, including mice, are a crucial component of kidney disease research; however, recent studies disprove the ability of autoanalyzer methods to accurately quantify plasma creatinine levels, an established marker of kidney disease, in mice. Therefore, we validated autoanalyzer methods for measuring blood urea nitrogen (BUN) and urinary albumin concentrations, 2 common markers of kidney disease, in samples from mice. We used high-performance liquid chromatography to validate BUN concentrations measured using an autoanalyzer, and we utilized mouse albumin standards to determine the accuracy of the autoanalyzer over a wide range of albumin concentrations. We observed a significant, linear correlation between BUN concentrations measured by autoanalyzer and high-performance liquid chromatography. We also found a linear relationship between known and measured albumin concentrations, although the autoanalyzer method underestimated the known amount of albumin by 3.5- to 4-fold. We confirmed that plasma and urine constituents do not interfere with the autoanalyzer methods for measuring BUN and urinary albumin concentrations. In addition, we verified BUN and albuminuria as useful markers to detect kidney disease in aged mice and mice with 5/6-nephrectomy. We conclude that autoanalyzer methods are suitable for high-throughput analysis of BUN and albumin concentrations in mice. The autoanalyzer accurately quantifies BUN concentrations in mouse plasma samples and is useful for measuring urinary albumin concentrations when used with mouse albumin standards.

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.

Increased instrument intelligence--can it reduce laboratory error?

Recent literature has focused on the reduction of laboratory errors and the potential impact on patient management. This study assessed the intelligent, automated preanalytical process-control abilities in newer generation analyzers as compared with older analyzers and the impact on error reduction. Three generations of immuno-chemistry analyzers were challenged with pooled human serum samples for a 3-week period. One of the three analyzers had an intelligent process of fluidics checks, including bubble detection. Bubbles can cause erroneous results due to incomplete sample aspiration. This variable was chosen because it is the most easily controlled sample defect that can be introduced. Traditionally, lab technicians have had to visually inspect each sample for the presence of bubbles. This is time consuming and introduces the possibility of human error. Instruments with bubble detection may be able to eliminate the human factor and reduce errors associated with the presence of bubbles. Specific samples were vortexed daily to introduce a visible quantity of bubbles, then immediately placed in the daily run. Errors were defined as a reported result greater than three standard deviations below the mean and associated with incomplete sample aspiration of the analyte of the individual analyzer Three standard deviations represented the target limits of proficiency testing. The results of the assays were examined for accuracy and precision. Efficiency, measured as process throughput, was also measured to associate a cost factor and potential impact of the error detection on the overall process. The analyzer performance stratified according to their level of internal process control The older analyzers without bubble detection reported 23 erred results. The newest analyzer with bubble detection reported one specimen incorrectly. The precision and accuracy of the nonvortexed specimens were excellent and acceptable for all three analyzers. No errors were found in the nonvortexed specimens. There were no significant differences in overall process time for any of the analyzers when tests were arranged in an optimal configuration. The analyzer with advanced fluidic intelligence demostrated the greatest ability to appropriately deal with an incomplete aspiration by not processing and reporting a result for the sample. This study suggests that preanalytical process-control capabilities could reduce errors. By association, it implies that similar intelligent process controls could favorably impact the error rate and, in the case of this instrument, do it without negatively impacting process throughput. Other improvements may be realized as a result of having an intelligent error-detection process including further reduction in misreported results, fewer repeats, less operator intervention, and less reagent waste.

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.

National standard for measurement of resting and ambulatory blood pressures with automated sphygmomanometers.

The Association for the Advancement of Medical Instrumentation develops voluntary standards for medical devices so that manufacturers might provide information on their product and basic safety and performance criteria that should be considered in qualifying the instrument for clinical use. American national standards are generated through a consensus process by committees consisting of experts in research, development, and design from user, industry, and government communities. Draft standards are made available for public review and may become American national standards after review by the American National Standards Institute. The first American national standard for electronic and automated sphygmomanometers was published in monograph form in 1987. The objective of the revised 1992 standard for electronic and automated sphygmomanometers is to provide updated labeling, safety, and performance requirements that help ensure that consumers and health care professionals are supplied with safe, accurate devices for the indirect measurement of blood pressure, including ambulatory blood pressure recorders. This standard permits validation of the automatic or electronic device by comparison with either direct, intra-arterial blood pressure measurements or the noninvasive cuff/stethoscope technique, based on Korotkoff sounds identified by individuals trained in auscultation. This summary report of the 1992 American national standard for automatic sphygmomanometers provides recommendations for the methods of comparison, statistical analysis of the data, presentation of the results, and criteria for acceptability. Users, researchers, and instrument designers should refer to the American national standard monograph for detailed requirements.

Importance of complete DNA digestion in minimizing variability of 8-oxo-dG analyses.

Estimates of 8-oxo-2'-deoxyguanosine (8-oxo-dG) in DNA vary at least one order of magnitude using different quantitative methods or even the same method. Our hypothesis is that an incomplete DNA hydrolysis to nucleosides by the conventional nuclease P1 (NP1) and alkaline phosphatase (AP) digestion system plays an important role in contributing to the variability of measurements using HPLC coupled with UV and electrochemical (EC) detection. We show here that factors, such as the amount of DNA, choice of enzymes, their activities, and incubation time, can affect DNA digestion and, thus, cause variability in 8-oxo-dG levels. The addition of DNase I and phosphodiesterases I and II to the NP1 + AP system improves the DNA digestion by completely releasing normal nucleosides and 8-oxo-dG, thereby reducing the interday variations of 8-oxo-dG levels. Diethylenetriamine pentaacetic acid (DTPA), an iron chelator, prevented background increases of 8-oxo-dG during DNA digestion, as well as during the waiting period in the autosampler when a batch of DNA samples is analyzed by HPLC. After optimization of the DNA digestion conditions, the interday variability of 8-oxo-dG measurements using commercially available salmon testes DNA (ST DNA) were 26% over a period of 2 years. Under these optimal conditions, our laboratory variability may contribute as little as 13% to the overall variability as shown by assessment of oxidative DNA damage in a population of smokers. Based on our results, we believe that the modified DNA digestion conditions will provide much more accurate 8-oxo-dG determinations and, thus, more reliable estimates of cancer risk.

A semi-automated microassay for complement activity.

A simple, automated microassay for the serum complement-dependent hemolytic activity is described here. In contrast to the traditional titration hemolysis assay, the new method depends on a single experimental step using a fixed volume of serum specimen and sheep erythrocytes. The assay is based on the change in light scattering properties of erythrocytes upon hemolysis. It relies on the spectrophotometric reading of microtiter well samples at 700 nm by using a microplate reader. The measured absorbance correlates proportionally with the extent of hemolysis. A good correlation between the results obtained using this technique and those obtained by the traditional CH50 titration method is observed. This simple procedure can be applied to the rapid, semi-quantitative diagnostic screening of complement activities of a large number of serum specimens.

Evaluation of an enzyme immunoassay for total IgE on a semi-automated analyser. A multicentre study.

Total serum IgE was measured by a semi-automated enzyme immunoassay on sera from normal and disease groups. Data from this investigation was analyzed in respect of precision, linearity, sensitivity and correlation with other test methods. Using human serum pools having values between 7 and 480 IU/ml, the intra-assay coefficient of variation ranged from 3.3 to 14.6% with an arithmetic mean of 6%. The inter-assay coefficient of variation on commercially supplied control sera ranged from 4.4 to 14.2%. In addition, tests were carried out on serially diluted samples to assess the linearity of the method, and on sera with IgE levels of less than 5 IU/ml in order to assess its sensitivity. It was shown that the technique being assessed was unaffected by the presence of lipid or haemoglobin or by the addition of bilirubin or any one of 46 commonly prescribed drugs each at double its toxic dose. There was good correlation between the semi-automated enzyme immunoassay technique and four other methods used during this study. This technique exhibits excellent specificity, reproducibility and a sensitivity well within clinical demands.

A high-sensitivity electrochemiluminescence-based detection system for automated PCR product quantitation.

A high-sensitivity nonisotopic system has been developed for post-PCR product detection. The probe-based detection system exploits a chemiluminescent reaction that takes place on the electrode surface in an electrochemical cell. The detection system incorporates a biotin-streptavidin capture reaction onto a solid support that permits fast post-PCR product detection at the attomole level. The system precision is within 5% relative standard deviation over a linear dynamic range of greater than three orders of magnitude. In this paper, the principles and features of the electrochemiluminescent-based detection system, together with its application to PCR product quantitation, are described in detail.

Analytic clinical laboratory precision. State of the art for twenty-nine analytes.

Relationships of concentration and coefficient of variation are described for 29 clinical laboratory analytes. Estimated mean regression curves and the standard deviations of individual laboratory coefficients of variation about the mean regression are calculated. Twenty-seven analytes showed a significant relation between concentration and coefficient of variation. State of the art precision is compared to medical goals. The average coefficient of variation for one analyte, calcium, fails to meet medical goals for manual methods. The distribution of individual laboratory precision above average state of the art figures is discussed. The proportion of laboratories failing to meet medical goals is large for osmolality, as well as manual calcium methods.

Use of anion gap for the quality control of electrolyte analyzers.

A simple model for the simulation of patient Na, CO2, Cl, and anion gap was formulated from patient electrolyte data. Analytical error, either random or systematic, was incorporated into the simulation of the electrolyte data and allowed study of the response of anion gap to error. Power functions, plots of probability of error detection vs. size of analytical error, were constructed and indicated a low probability of error detection when single patient specimens with abnormal anion gaps were reanalyzed. These power functions showed that pooling of the anion gap data by averaging consecutive anion gaps resulted in a high probability for detecting systematic error. We recommend, as a useful quality control procedure, averaging at least eight consecutive anion gaps and testing for a significant difference between the average and the established mean gap.

Serum creatinine. A CAP survey.

The results of the 1976--1977 College of American Pathologists Survey of serum creatinine measurements performed by more than 5,000 laboratories are presented. The most widely used method employs the colorimetric measurement of the alkaline picrate-creatinine (Jaffe) reaction. In general, all manual and automated systems yielded comparable creatinine concentrations except the centrifugal analyzers, which manifested a consistently high bias. Interlaboratory variation was lowest for continuous-flow and the DuPont discrete systems. Lloyd's reagent resulted in a clinically insignificant reduction of creatinine concentration in lyophilized sera.

Simple procedures can markedly enhance automated immunoassay performance.

Theoretically, optimal performance for an immunoassay system is achieved when both the interassay and within-run precisions are identical. Using the Ciba Corning ACS:180 automated immunoassay system, the authors made two simple changes to the operating procedures that allowed near-optimal analytic performance (as assessed with the interassay coefficient of variation determined by the protocol of the National Committee for Clinical Laboratory Standards) for four of six hormones: thyroid-stimulating hormone, luteinizing hormone, prolactin, and human chorionic gonadotropin. At low hormone concentrations, the 20% interassay coefficients of variation for the hormones assayed were as follows: free tetraiodothyronine, 1.74 pM; thyroid-stimulating hormone, .033 mIU/L; luteinizing hormone, .21 U/L; follicle-stimulating hormone, .69 U/L; prolactin, 5.03 mU/L; and human chorionic gonadotropin, 1.52 mU/L. The operational enhancements improved the analytic performance of the assay for all hormones assessed compared with the performance of previously used isotopic immunoassays.