Total Allowable Error Research Articles

The effect of different forms of heparin on point-of-care blood gas analysis.

Point-of-care blood gas analysis plays an integral role in the management of critically ill and injured patients presenting to the emergency department (ED). While the use of specially manufactured syringes containing electrolyte-balanced dried heparin is recommended when processing these specimens, alternatives including manually self-prepared syringes washed with liquid heparin or heparin vacutainers are still often used. To assess the effect of two concentrations of liquid heparin and the use of heparin vacutainers on the reliability of blood gas analysis results compared with the recommended standard of dried heparin syringes in the ED setting. Blood samples were drawn from 54 patients attending a tertiary-level hospital ED. Individual samples were distributed equally among each of four different collection devices: a dried heparin syringe, self-prepared syringes washed separately with 1 000 IU/mL and 5000 IU/mL liquid heparin, and a heparin vacutainer. Results obtained from the standard dried heparin syringes were compared with those from the other three methods. For both the liquid heparin cohorts, partial pressure of carbon dioxide (pCO2), potassium (K+), sodium (Na+), ionised calcium (iCa2+) and haemoglobin had >20% of results falling beyond the total allowable error. iCa2+ and K+ results were most affected in the 5 000 IU/mL cohort and iCa2+ and Na+ in the 1 000 IU/ml cohort. pCO2, pH and iCa2+ were the most significantly affected in the heparin vacutainer cohort. Use of liquid heparin can result in significant negative bias in the majority of blood gas analytes, especially electrolytes. Heparin vacutainer use can result in unacceptable variations in the respiratory analytes. While standard dried heparin syringes may not always be available, it is of vital importance that practitioners be aware of these biases and limitations when using substitutes.

Evaluation of analytical performance specifications of routine clinical biochemistry tests with biological variation-based total allowable error (TEa) criteria

Evaluation of analytical performance specifications of routine clinical biochemistry tests with biological variation-based total allowable error (TEa) criteria

Performance Standards for Quality Control Systems

<h3>ABSTRACT</h3> Standard statistical quality control (QC) has been around since its introduction in 1950 by Levey and Jennings. Today, while most laboratories use standard statistical QC processes, with or without Westgard multi-rules to evaluate quality, few incorporate performance standards in their QC systems. With performance standards, the quality level of each test is determined on a sigma scale. This guides the selection of optimal QC frequency and rules to monitor the analytical system. QC rules are selected based on the sigma score and are specific to each test. While a single rule (1_3s) is sufficient to efficiently monitor tests with sigma quality at or above 6, a more stringent rule (1_3s/2_2s/R_4s/4_1s) is required for those performing at four sigma. The comparison of analytical total error (TE) to the total error allowable (TEa) helps ensure that the system is operating within the defined quality specifications; therefore, accurate patient results are produced.

Validation of the Friedewald formula for the estimation of low density lipoprotein cholesterol in a sub-Saharan African population

Introduction : low density lipoprotein cholesterol (LDL-C) levels are used to estimate cardiovascular disease (CVD) risk and to guide prescriptions. To circumvent the challenges of direct LDL-C measurement, guidelines recommend the use of Friedewald formula derived LDL-C levels. Despite reported limitations of this formula, its validity in sub-Saharan Africans has not been adequately investigated. The objective was to assess the validity of the Friedewald formula derived against directly measured LDL-C in adult Cameroonians. Methods : we reviewed the fasting lipid profiles of 2500 patients, performed between March 2012 and January 2016 using enzymatic colorimetric method (reference), at the Douala General Hospital laboratory. The Friedewald formula was used to calculate LDL-C from total cholesterol, high density lipoprotein cholesterol and triglyceride levels. Calculated LDL-C values were compared to the reference values and clinical significance of differences between the two methods was assessed using total error allowable (TEa). Results : the difference between means of Friedewald-calculated and the reference LDL-C values was neither statistically nor clinically significant (3.33±1.51 vs. 3.33 ± 1.25 mmol/l; p = 0.704). The calculated LDL-C correlated positively with the measured LDL-C value (r = 0.749) and both methods showed a good agreement on Bland-Altman plot. Conversely, there was only moderate agreement (kappa=0.478, 95% CI: 0.455-0.502) between the two values in the stratification of cardiovascular risk according to the National Cholesterol Education Programme/Adult Treatment Panel III. Consequently, 40.6% of the participants were misclassified. Conclusion : Friedewald formula is technically accurate but has a modest clinical accuracy which can translate into a substantial misclassification of patients’ cardiovascular risk and subsequent inappropriate therapeutic decisions.

Validation of the Friedewald formula for the estimation of low density lipoprotein cholesterol in a sub-Saharan African population

BackgroundLow density lipoprotein cholesterol (LDL-C) levels are used to estimate cardiovascular disease (CVD) risk and to guide prescriptions. To circumvent the challenges of direct LDL-C measurement, guidelines recommend the use of Friedewald formula derived LDL-C levels. Despite reported limitations of this formula, its validity in sub-Saharan Africans has not been adequately investigated. ObjectiveTo assess the validity of the Friedewald formula derived against directly (homogeneous) measured LDL-C in adult Cameroonians. MethodsWe reviewed the fasting lipid profiles of 2500 patients, performed between March 2012 and January 2016 using enzymatic colorimetric method (reference), at the Douala General Hospital laboratory. The Friedewald formula was used to calculate LDL-C from total cholesterol, high density lipoprotein cholesterol and triglyceride levels. Calculated LDL-C values were compared to the reference values, and clinical significance of differences between the two methods was assessed using total error allowable (TEa). ResultsThe difference between means of calculated and the reference LDL-C values was neither statistically nor clinically significant (3.33±1.51 vs. 3.33±1.25mmol/l; p=0.704). The calculated LDL-C correlated positively with the measured LDL-C value (r=0.749) and both methods showed a good agreement on Bland-Altman plot. Conversely, there was only moderate agreement (kappa=0.478, 95% CI: 0.455–0.502) between the two values in the stratification of cardiovascular risk according to the National Cholesterol Education Program/Adult Treatment Panel III. Consequently, 40.6% of the participants were misclassified. ConclusionFriedewald formula is technically accurate but has a modest clinical accuracy which can translate into a substantial misclassification of patients' cardiovascular risk and subsequent inappropriate therapeutic decisions.

Validation of 2 point-of-care meters for measuring triglycerides in chickens using whole blood and plasma.

Disorders of the avian reproductive tract are common, yet monitoring their resolution presents a diagnostic dilemma. Reproductive hormones such as luteinizing hormone or estrogen are the best reflection of reproductive status, but the required sample volumes and lack of reference intervals limit their clinical utility. An alternative analyte is blood triglyceride, the concentration of which rises markedly during sustained estrogen release from the ovary. Portable meters for measuring human blood triglyceride concentration offer the advantage of using minimal sample volumes, but these have not been validated for use in birds. We assessed the precision and accuracy of 2 portable meters for measuring blood triglyceride concentration in pooled whole blood and plasma from chickens ( n = 42), and performed method comparison using a reference analyzer and determined total error. Within-run repeatability was fair-to-excellent using whole blood and plasma (range: 2.5-11.5%), and between-run repeatability using plasma was similar (3.1-12.2%). The meters performed well in recovery and dilution studies in which almost all readings fell within the preset requirement of 75-125%. Correlations between each meter, using whole blood and plasma, and the reference analyzer, using plasma only, were high to very high (0.86-0.98). Bias determined by Bland-Altman analysis was similar between whole blood and plasma for each meter, yet markedly different between the meters. The calculated total observed error was consequently within our pre-set total allowable error of 25% for one meter but not the other, indicating the requirement for a meter-specific reference interval.

Standardization of Urine Albumin Measurements: Status and Performance Goals.

Urine albumin is a key laboratory test used for classification, assessment of risk, and monitoring treatment of patients with chronic kidney disease. Urine albumin measurement results are not standardized among different measurement procedures. Consequently, clinical guidelines using fixed decision values for urine albumin cannot be applied consistently. Isotope dilution mass spectrometry reference measurement procedures and certified reference materials are being developed to enable standardization of immunoassay measurement procedures for urine albumin. A previous report determined calibration bias was the major error source for differences in results among different measurement procedures for urine albumin. Performance goals for between-day precision, ≤6% CV above 15 mg/L, and for specimen-specific effects, ≤6% CV, were established on the basis of the performance capability of current measurement procedures. The biological variation model was used to estimate a total allowable error of ≤24%-30% and from that the goal for bias of ≤7%-13%. A reference system of higher-order certified reference materials and reference measurement procedures is being developed to enable standardization of urine albumin measurement results. Goals have been established for total allowable error, specimen-specific effects, imprecision, and bias to facilitate efforts to standardize urine albumin measurement results.

The application of sigma metrics quality models in quality management of clinical biochemistry laboratory

Objective To improve the quality of clinical biochemistry laboratory by quality indicators of pre-analytical, analytical, post-analytical phase and the whole process. Methods Analytical Phase: The Sigma values of items were calculated, applying the equation Sigma=(TEa%-Bias%)/CV%. Total allowable error (TEa) is from analyticalal specification defined in WS/T403-2012 of China, Bias% is from the evaluation results of National Center for Clinical Laboratory (NCCL) trueness verification PT series and CV% is from internal quality control data during the last 6 months in our lab. Normalized Sigma metrics plot was made to evaluate the analysis performance and the quality control strategies were designed accordingly. The quality goal indexes (QGI) were also calculated to propose improvement measures for items below 6 Sigma. Quality indicators of pre-, post-analytical and whole analytical phase, such as quality of specimen, critical value notification, critical value notification in time, TAT of hs-cTnT, TAT of emergency biochemical items, rewrite of laboratory reports and unacceptable performance in EQA-PT were measured in Sigma metrics too. The Sigma metrics changes before and after taking improvement measures were compared to conform the effectiveness. Results The average Sigma value of 17 biochemical tests was 5.29, of which 8 items (UA, K, ALP, CK, AMY, AST, TG, Na) achieved excellent to world class level (≥5 Sigma), 6 items (LDH, Cre, TC, ALT, Mg, Glu) achieved marginal to good level (5>Sigma≥3), BUN performed poorly (3>Sigma≥2), Ca, TP performed unacceptably (Sigma<2) with serious quality defects. The Sigma values of unacceptable specimen, critical value notification, critical value notification in time, unacceptable turn around time (TAT) of hs-cTnT, unacceptable turn around time (TAT) of emergency biochemical items, rewrite of laboratory reports, unacceptable performance in EQA-PT were 4.17, 3.60, 2.75, 1.72, 3.27, 4.52, 3.33 respectively, rising to 4.30, 4.30, 2.90, 2.45, 3.75, 4.80, 3.60 accordingly after improvement. Conclusions Sigma metrics is potentially an ideal approach for clinical biochemistry laboratories management, which is helpful to find out problems, put forward improvement measures, and confirm the effectiveness, so as to achieve the purpose of continuous quality improvement.(Chin J Lab Med, 2017, 40: 727-732) Key words: Clinical chemistry tests; Quality control; Laboratories, hospital; Quality indicators, health care; Quality improvement

Evaluation of clinical chemistry tests in emergency laboratory by sigma metrics

Abstract Aim Emergency department laboratories, besides from giving accurate results, should be quick enough in order not to delay patient care. Giving fast results doesn’t mean to ignore quality, rather it should always be improved to prevent erroneous results. Six sigma is a modern assessment of quality which is used to determine the analytical performance. Our aim was to evaluate the analytical performance of clinical chemistry tests in our emergency department laboratory by using sigma metrics. Materials and methods Our study was performed by using the internal and external quality assessment data of 13 clinical chemistry tests of emergency laboratory. Sigma levels were calculated using bias, coefficient of variation and total allowable error (TEa) ratios of CLIA, Ricos, Rilibak and Turkey. Results Sigma levels of various tests (CK, amylase, ALT, AST, urea, creatinine, total bilirubin, sodium and chloride) were found to be ≥6 according to different TEa’s, whereas the performance of sodium, potassium and chloride were unsatisfactory, according to TEa’s of CLIA, Ricos and Rilibak. Conclusion Since most of our sigma values were found to be over 3, the analytical performance of clinical chemistry tests was thought to be acceptable and our laboratory can be regarded as a qualified emergency laboratory.

The Evaluation of Analytical Performance of Immunoassay Tests by using Six-sigma Method.

SummaryBackgroundThe Six-Sigma Methodology is a quality measurement method in order to evaluate the performance of the laboratory. In the present study, it is aimed to evaluate the analytical performance of our laboratory by using the internal quality control data of immunoassay tests and by calculating process sigma values.MethodsBiological variation database (BVD) are used for Total Allowable Error (TEa). Sigma values were determined from coefficient of variation (CV) and bias resulting from Internal Quality Control (IQC) results for 3 subsequent months. If the sigma values are ≥6, between 3 and 6, and <3, they are classified as »world-class«, »good« or »un - acceptable«, respectively.ResultsA sigma value >6 was found for TPSA and TSH for the both levels of IQC for 3 months. When the sigma values were analyzed by calculating the mean of 3 months, folate, LH, PRL, TPSA, TSH and vitamin B12 were found >6. The mean sigma values of CA125, CA15-3, CA19-9, CEA, cortisol, ferritin, FSH, FT3, PTH and testosteron were >3 for 3-months. However, AFP, CA125 and FT4 produced sigma values <3 for varied months.ConclusionWhen the analytical performance was evaluated according to Six-Sigma levels, it was generally found as good. It is possible to determine the test with high error probability by evaluating the fine sigma levels and the tests that must be quarded by a stringent quality control regime. In clinical chemistry laboratories, an appropriate quality control scheduling should be done for each test by using Six-Sigma Methodology.

Aplicación de metas analíticas y modelo Seis Sigma en la evaluación del control de calidad de Química Clínica

IntroductionWith the aim of providing clinically relevant results, the clinical laboratory must implement a sufficiently good internal quality control system in order to achieve analytical goals with the highest possible standards. Materials and methodsA retrospective, descriptive, and longitudinal study was performed in order to study the internal quality control results of the Clinical Chemistry area of a Mexican laboratory obtained during the period from July to December 2016. ResultsThe Clinical Laboratory Improvement Amendments (CLIA) goals of maximum total allowable error were achieved in 100% of the analytes studied. In the case of biological variation goals, desirable or optimal goals were achieved for in 89% of the analytes studied, with inferior results being obtained in these analytes with a low biological variability index. Finally, as regards the results of sigma values, our results varied considerably depending on the analytical specifications used, achieving the lowest values in those analytes with the lowest biological variability index. ConclusionsBased on our results we can suggest that an adequate quality control model in Clinical Chemistry could initially include the establishment of analytical specifications based on CLIA for those analytes with low biological variation, and the desirable goals of biological variation for the rest of the analytes. Both goals can be achieved by the instruments used in this study.

Quality specifications of routine clinical chemistry methods based on sigma metrics in performance evaluation.

Sigma metrics were applied to evaluate the performance of 20 routine chemistry assays, and individual quality control criteria were established based on the sigma values of different assays. Precisions were expressed as the average coefficient variations (CVs) of long-term two-level chemistry controls. The biases of the 20 assays were obtained from the results of trueness programs organized by National Center for Clinical Laboratories (NCCL, China) in 2016. Four different allowable total error (TEa) targets were chosen from biological variation (minimum, desirable, optimal), Clinical Laboratory Improvements Amendments (CLIA, US), Analytical Quality Specification for Routine Analytes in Clinical Chemistry (WS/T 403-2012, China) and the National Cholesterol Education Program (NECP). The sigma values from different TEa targets varied. The TEa targets for ALT, AMY, Ca, CHOL, CK, Crea, GGT, K, LDH, Mg, Na, TG, TP, UA and Urea were chosen from WS/T 403-2012; the targets for ALP, AST and GLU were chosen from CLIA; the target for K was chosen from desirable biological variation; and the targets for HDL and LDL were chosen from the NECP. Individual quality criteria were established based on different sigma values. Sigma metrics are an optimal tool to evaluate the performance of different assays. An assay with a high value could use a simple internal quality control rule, while an assay with a low value should be monitored strictly.

Comparison of a full-spectrum multi-analyte clinical analyser with six reference instruments using canine and feline blood samples

In this study, we report the characterisation of a novel centrifugation and spectrum-integrated veterinary clinical analyser, the AmiShield&lt;sup&gt;TM&lt;/sup&gt;, which has been developed for the multiplex measurement of biochemical, electrolyte and immunoassay parameters in a point-of-care testing environment. The aims of this study were to evaluate the analytical performance of the AmiShield&lt;sup&gt;TM&lt;/sup&gt; and to compare it with six reference instruments using clinical blood samples. Two hundred and four canine and 120 feline blood samples collected from veterinary teaching hospitals were analysed in parallel using the AmiShield and appropriate reference instruments. All results were evaluated separately for canine and feline specimens. The instrument’s analytical performance was evaluated initially for short- and long-term precision, bias, and observed total error using quality control material. This was followed by comparison of clinical specimens on the AmiShield analyser in parallel with the Vitros and Hitachi for biochemical parameters, VetScan and SNAPshot for total bile acids, and VetLyte and Biolyte for electrolytes. Overall, the AmiShield analyser’s performance met the standards of the American Society for Veterinary Clinical Pathology for total allowable error for most analytes, and can be considered suitable for use in veterinary clinical practices. Using canine samples, excellent correlation coefficients (r ≧ 0.92) were identified for 14 analytes of various categories including glucose, total protein, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total bilirubin, amylase, blood urea nitrogen, creatinine, phosphorus, Na&lt;sup&gt;+&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;, Cl&lt;sup&gt;–&lt;/sup&gt; and total bile acid, while good correlations (0.91 ≧ r ≧ 0.80) were recorded for albumin (r = 0.91). Bland-Altman difference plots also showed agreement (greater than 95% within Limits of Agreement) for glucose, total protein, albumin, alanine aminotransferase, alkaline phosphatase, total bilirubin, amylase, blood urea nitrogen, creatinine, Na&lt;sup&gt;+&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;, Cl&lt;sup&gt;–&lt;/sup&gt; and total bile acid between AmiShield and the reference instruments. However, aspartate aminotransferase and phosphorus exhibited higher outliers, implying potential problems associated with matrix interferences such as lipemic samples, which warrant further study. This study demonstrates that the AmiShield compares favourably with standard reference instruments, and the new device generated data of high quality for most analytes in clinical canine and feline samples. The capability of reliably measuring multi-category analytes in one device using minute amounts (170 μl) of whole blood and short turn-around times (&amp;lt; 15 min) underlines the high potential of the device as a good alternative in-house diagnostic application.

Study and analysis of national current status and problems of anticoagulant proteins assay

Objective: To investigate current status and problems of anticoagulant proteins assay in domestic laboratories so as to provide suggestions for implementing the standardization and quality improvement. Methods: Two hundred and seventy-four laboratories those had developed or prepared to do anticoagulant proteins assay were selected from one thousand and five hundred participants in the national coagulation screening External Quality Assessment(EQA) program by an internet survey and then a questionnaire and quality control materials were sent to them to carry out a further survey. The questionnaire information was analyzed statistically. The results of quality control materials were grouped by the reagents and the average, median, standard deviation(s), coefficient variation(CV) of each group were calculated. The deviations or percentage deviations were determined by comparing the results of each laboratory to the target defined as the peer-group median after exclusion of outliers, and then the pass rates were calculated based on the criterion of RCPA, DGKL and the allowable total error based on biological variation. Results: Two hundred and thirty-five questionnaires were collected. The number of laboratories testing antithrombin(AT), protein C(PC) and protein S(PS) activity were 194, 63 and 50 respectively. The instruments and reagents were mainly from abroad (more than 96%), the matching rate of which were above 94%. For AT, PC and PS activity testing, there were 30.4%, 33.3%, 34.0% of laboratories did not perform verification assays respectively, and 8.8%, 7.9%, 14.0% of laboratories did not renew calibration curve when the reagent lots were changed. 11.3%, 17.5%, 16.0% of laboratories didn't run internal quality control, and 34.9%, 26.9%, 21.4% of laboratories only performed a single level of quality control. 4.1% of laboratories set the reference intervals of AT activity according to different age groups, and the percentage of that of PC and PS activity were 1.6% and 2.0%. 16.0% of laboratories set the reference interval of PS activity by sex. For normal control materials, the CV of AT, PC and PS activity results were 5.7%-12.9%, 4.2%-7.7% and 18.4%-33.1% while the CV for abnormal level were 13.3%-38.3%, 6.1%-14.4% and 31.5%-34.5% respectively. The pass rate was different when it was judged by different criteria. A suitable criterion for each item should be selected according to the concentration level of quality control materials. Conclusion: The comparability between laboratory results are not satisfactory and in order to promote quality improvement, it is necessary to develop guidelines, organize trainings and establish a national EQA scheme.

A comparison between China-made Mindray BS-2000M biochemical analyzer and Roche cobas702 automatic biochemical analyzer

ObjectiveTo assess the China-made equipment Mindray BS-2000M biochemical analyzer and explore the comparability between the results of the sixteen test parameters detected by Mindray BS-2000M biochemical analyzer and by imported equipment Roche cobas702 automatic biochemical analyzer. MethodsIn line with the American Clinical Laboratory Standardization Committee (NCCLS) document EP9-A2, Switzerland Roche cobas702 biochemical analyzer was used as a comparison system, while the Mindray BS-2000M served as an experimental system. Sixteen biochemical parameters from forty cases at different levels were tested at the same time. The correlation coefficient(r), linearity regression equation and absolute deviation (SE) and relative deviation (SE%) of test detection system (Y) and control detection system (X) at different medical decision levels were calculated. The clinical acceptability and comparability between different detection systems were tested according to the standard of allowed total error of American Clinical Proficiency Testing Laboratory Improvement Amendments (CLIA'88). ResultsThe test results of the sixteen parameters between the two different biological detection systems were well-correlated (r2 ≥0.95, p<0.01). Linearity study showed acceptable linearity ranges for all the parameters. The relative deviation SE% of sixteen biochemical parameters at different medical decisions levels, excepting relative deviation of TP at two levels and TBIL at one level was greater than 1/2 CLIA 88 allowable total error, while the relative deviation or absolute deviation of the rest of the test parameters at their medical decision levels was less than 1/2CLIA88 predetermined allowable total error, and the total pass rate was 93%, so the China-made equipment Mindray BS-2000M biochemical analyzer may be clinically acceptable. ConclusionMindray BS-2000M has achieved the desirable photometry technical and analytical performance, and can therefore be used in modern clinical laboratories.

Objective evaluation of analyzer performance based on a retrospective meta-analysis of instrument validation studies: point-of-care hematology analyzers.

Information on quality requirements and objective evaluation of performance of veterinary point-of-care analyzers (POCAs) is scarce. The study was aimed at assessing observed total errors (TEobs s) for veterinary hematology POCAs via meta-analysis and comparing TEobs to allowable total error (TEa ) specifications based on experts' opinions. The TEobs for POCAs (impedance and laser-based) was calculated based on data from instrument validation studies published between 2006 and 2013 as follows: TEobs = 2 × CV [%] + bias [%]. The CV was taken from published studies; the bias was estimated from the regression equation at 2 different concentration levels of measurands. To fulfill quality requirements, TEobs should be < TEa . Measurands were considered as globally acceptable if > 60% of analyzers showed TEobs < TEa . Six studies evaluating 11 analyzers and 5 studies evaluating 5 analyzers were included for canine and feline hematology variables, respectively. For the CBC, TEobs was < 15% for canine and < 13% for feline measurands, except for HGB and platelet counts. Measurands of the CBC, excluding differential WBC and platelet counts, and HGB concentration were considered globally acceptable. For most of the cell types in the WBC differential count, TEobs was > TEa (data from 3 analyzers). This meta-analysis is considered a pilot study. Experts' requirements (TEobs < TEa ) were fulfilled for most measurands except HGB (due to instrument-related bias for the ADVIA 2120) and platelet counts. Available data on the WBC differential count suggest an analytic bias, so nonstatistical quality control is recommended.

Validation of a hand-held point of care device for lactate in adult and pediatric patients using traditional and locally-smoothed median and maximum absolute difference curves

BackgroundLactate is commonly used in septic patients and is a viable biomarker for trauma patients. Its pre-hospital use could assist triaging and managing patients with these conditions. MethodsWe evaluated the analytical performance of the point-of-care (POC) StatStrip Xpress Lactate Meter (Nova Biomedical) and compared it to the ABL 800 (Radiometer). We measured lactate in 250 adult and 250 pediatric whole blood samples in 2 laboratories. The performance of the POC meter was assessed by traditional linear regression and Bland-Altman plots, and locally-smoothed (LS) median absolute difference and maximum absolute difference (MAD and MaxAD) curves. ResultsThe StatStrip was linear with acceptable reproducibility at clinically relevant concentrations. Correlation with the ABL800 showed a negative bias for both populations with slope, bias ±SD (% bias) of 0.78, −0.4±0.7 (−14.5%) in children and 0.80–0.3±0.6 (−13.3%) in adults. The proportional bias appeared more significant at concentrations >4mmol/l (36.0mg/dl). The StatStrip misclassified 7.6 and 8.8% pediatric and adult samples, respectively, to lower risk categories defined using guidelines driven cut-offs. The LS MAD curves identified one breakout, concentration where the LS MAD exceeds the total allowable error limit of 0.3mmol/l (2.7mg/dl), at lactate concentrations of 3.8 and 3.2mmol/l (34.2 and 28.8mg/dl) in the pediatric and adult curves, respectively. Breakthroughs, points at which the LS MaxAD curve exceeds the 95th percentile of MaxADs, occur at concentrations above 7.5mmol/l (67.6mg/dl) for both populations where the performance of the POC meter became erratic. We concluded that if serial lactate measurements are performed, the same method should be used for baseline and follow up measurements. The LS MAD and LS MaxAD curves allowed visual and quantitative mapping of the performance of the lactate POC meter over the range of concentrations measured. ConclusionsThis approach seems useful for the identification of points at which the performance of a POC meter differs significantly from a comparison method and thresholds of poor analytical performance.

Appropriateness of on-combine moisture measurement for the management of harvesting and postharvest operations and capacity planning in grain harvest

Grain moisture content is an important factor for the management of harvesting and postharvest operations and for capacity planning in grain harvest, storage and preservation, and a basis for pricing in grain trade. The advantage of rapid and non-destructive on-combine moisture content determination is set against the disadvantage of lower measurement accuracy. The objectives of this study are to determine the agreement of on-combine grain moisture measurement with laboratory measurement methods, and to assess the suitability of on-combine grain moisture measurement. The appropriateness of on-combine measurement of grain moisture content for the management of harvesting and postharvest operations and capacity planning by maintaining a defined acceptable level of disagreement was also investigated. On-combine moisture measurement (OMC) was compared with two dry-oven methods and two capacitive moisture sensors used in laboratories, in each case for unground and ground grain. Field trials with on-combine moisture measurements and manual sampling were carried out on two farms in Germany in 2014. A total area of 514 ha with 201 manual samples was used for the investigations. The assessment of on-combine moisture measurement indicated that the on-combine approach is suitable for quantifying the variability of grain moisture content. The deviation between indirect laboratory methods and on-combine moisture meters was sufficient to determine the allowable total error that agreed with the defined relative error of two percentage points moisture content. In combination with fuzzy classification of grain moisture measurements, the on-combine moisture meters are suitable for process control and capacity planning for grain harvest and preservation.

Analytic and quality control validation and assessment of field performance of a point‐of‐care chemistry analyzer for use in the White rhinoceros

A chemistry point-of-care analyzer would be useful for evaluating injured wildlife, particularly White rhinoceros (Ceratotherium simum) that survive poaching attempts. The IDEXX VetTest could be suitable, but species-specific validation, development of a statistical quality control (QC) strategy, and evaluation under field conditions are necessary. The objectives were to (1) validate the VetTest for the White rhinoceros, (2) perform QC validation on the VetTest and generate a statistical QC strategy, and (3) apply this QC strategy to monitor performance under typical field conditions. Differences between White rhinoceros heparin plasma and serum, short-term imprecision, and reportable range using rhinoceros plasma and long-term imprecision using commercial quality control material (QCM) were assessed against prescribed total allowable error (TEa ) for up to 15 analytes. Quality control validation was performed using data from the long-term imprecision study and TEa . A QC strategy using QCM was developed and used to monitor performance under field conditions. Imprecision was acceptable for all analytes except for ALP, ALT, and AST at low activities. The reportable range for AST and LDH differed from the manufacturer's specifications. Eleven analytes were suitable for statistical QC using the 13s rule, 3 using the 2s rule; ALP was not suitable. In the field, observed error was < TEa for all 15 analytes and the sigma metric was > 3.0 for 12 analytes. The VetTest is suitable for use in the White rhinoceros. Statistical QC is possible for most analytes and useful for evaluation of field performance.

Expressing analytical performance from multi-sample evaluation in laboratory EQA.

To provide its participants with an external quality assessment system (EQAS) that can be used to check trueness, the Dutch EQAS organizer, Organization for Quality Assessment of Laboratory Diagnostics (SKML), has innovated its general chemistry scheme over the last decade by introducing fresh frozen commutable samples whose values were assigned by Joint Committee for Traceability in Laboratory Medicine (JCTLM)-listed reference laboratories using reference methods where possible. Here we present some important innovations in our feedback reports that allow participants to judge whether their trueness and imprecision meet predefined analytical performance specifications. Sigma metrics are used to calculate performance indicators named 'sigma values'. Tolerance intervals are based on both Total Error allowable (TEa) according to biological variation data and state of the art (SA) in line with the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Milan consensus. The existing SKML feedback reports that express trueness as the agreement between the regression line through the results of the last 12 months and the values obtained from reference laboratories and calculate imprecision from the residuals of the regression line are now enriched with sigma values calculated from the degree to which the combination of trueness and imprecision are within tolerance limits. The information and its conclusion to a simple two-point scoring system are also graphically represented in addition to the existing difference plot. By adding sigma metrics-based performance evaluation in relation to both TEa and SA tolerance intervals to its EQAS schemes, SKML provides its participants with a powerful and actionable check on accuracy.