Application and optimization of reference change values for Delta Checks in clinical laboratory

BACKGROUND

Delta check is a patient-based QC tool for detecting errors by comparing current and previous test results of patient. Reference change value (RCV) is adopted in guidelines as method for delta check, but the performance is not verified. We applied RCV-based delta check method to patients' data and modified for application.

MATERIALS AND METHODS

Reference change value were calculated using results of internal QC materials and biological variation data. Test results of 17 analytes in inpatients, outpatients, and health examination recipients were collected. The detection rates of currently used delta check method and those of RCV-based method were compared, and the methods were modified.

RESULTS

Reference change value-based method had higher detection rates compared to conventional method. Applied modifications reduced detection rates. Removing the pairs of results within reference interval reduced detection rates (0.42% ~ 10.92%). When RCV was divided by time interval, the detection rates were similar to prior rates in outpatients (0.19% ~ 1.34%). Using RCV multiplied by twice the upper limit of reference value as cutoff reduced the detection rate (0.07% ~ 1.58%).

CONCLUSIONS

Reference change value is a robust criterion for delta check and included in clinical laboratory practice guideline. However, RCV-based method generates high detection rates which increase workload. It needs modification for use in clinical laboratories.

[An investigation of non-specific reactions in measurement of plasma (1-->3)-beta-D-glucan]

We investigated the detection of non-specific reaction in measurement of plasma (1-->3)-beta-D-glucan (beta-glucan) by alkaline treatment, chromogenic automated kinetic assay (alkaline-kinetic assay) and dilution and heating method, chromogenic endpoint assay (dilution heating endpoint assay). In this study, we reexamined the values of beta-glucan by both methods with and without 4-amidinophenyl benzoate hydrochloride (APB) as protease inhibitor that blocks Limulus reaction in the 142 serum samples from 142 patients who had been treated and measured beta-glucan in Kawasaki medical school hospital between January 1999 and May 1999. Non-specific reactions were judged by the calculated value under APB additive condition. The non-specific reactions were found in 135 of total 142 samples (95.1%) in the alkaline-kinetic assay while no non-specific reactions were recognized in dilution heating endpoint assay. The alkaline-kinetic assay has been used widely and been evaluated it's usefulness because of good sensitivity. However, we found very high frequency of nonspecific reaction in this method. Further studies are needed to define the reasons of non-specific reaction. On the other hand, although non-specific reactions were not detected in dilution heating end-point assay, it's clinical utilities should be evaluated in future clinical studies.

Peritoneal and Pleural Fluid Chemistry Measurements Performed on Three Chemistry Platforms

BACKGROUND

Chemistry testing is requested for body fluid (BF) specimens despite the lack of assays approved by the US Food and Drug Administration (FDA). The criteria for categorizing fluids as transudate or exudate are not validated across analyzers.

OBJECTIVE

To compare BF chemical analysis and classification by different analyzers.

METHODS

We analyzed 10 pleural and 18 peritoneal fluids with corresponding plasma specimens using the Vitros 5,1 FS; Abbott ARCHITECT ci8200; and Roche Modular P platforms. Total protein (TP) and lactate dehydrogenase (LDH) were measured for pleural fluids. Light's criteria were applied. Albumin was measured for peritoneal specimens, and the plasma-ascites-albumin gradient was calculated.

RESULTS

TP results showed agreement. The Vitros LDH assay produced higher fluid:plasma ratios. Classification by Light's criteria resulted in 1 discrepancy (ARCHITECT). Albumin results showed agreement. There were 2 discrepant gradient interpretations (Vitros).

CONCLUSIONS

These data suggest that analyses of pleural and peritoneal fluids using these platforms are diagnostically interchangeable.

Confirmation of neonatal screening: reference intervals and evaluation of methodological changes in TSH measurement

Neonatal reference values for serum thyrotropin are scarce and comprise only small numbers of patients. During 2006, changes were made in IMMULITE kits for TSH measurement. To validate methodological changes, 80 serum samples from patients were evaluated and to establish reference intervals, 334 neonates and infants were analyzed (divided into 4 groups). Group 1 (G1) (48-72 h of life) (n=153), group 2A (G2A) (7-10 days of life) (n=65), group 2B (G2B) (11-14 days of life) (n=35), group 3 (G3) (28-40 days of life) (n=81). Current kits overestimate TSH results by 26 to 37%; TSH (mIU/L) reference intervals (percentile 2.5-97.5) were G1 (1.1-12.7), G2A (1.8-9.8), G2B (1.1-7.1) (p < 0.03 vs. G2A), G3 (1.2-6.9). We suggest that during the second week of life, reference values should be divided into an early stage and a late stage, at least, for there to be an adequate interpretation of borderline measurements in newborn thyroid screening.

Accuracy of the 13C-glucose breath test to identify insulin resistance in non-diabetic adults

AIMS

To assess the validity of the ¹³C-glucose breath test (¹³C-GBT) to identify insulin resistance (IR) in non-diabetic individuals, using hyperinsulinemic-euglycemic clamps as gold standard. This validity was compared with that of other IR surrogates.

METHODOLOGY

Non-diabetic adults were studied in a cross-sectional design. In a first appointment, oral glucose tolerance tests were conducted simultaneously with ¹³C-GBTs. Oral 75 g glucose dissolved in 150 ml water, followed by 1.5 mg/Kg body weight U-¹³C-glucose dissolved in 50 ml water, was administered. Breath and blood samples were collected at baseline and at 30-min intervals. The percentages of glucose-oxidized dose at given periods were calculated. Clamps were conducted a week later. A clamp-derived M value ≤ 6.0 mg/kg*min was used as cut-off. ROC curves were constructed for ¹³C-GBT, fasting insulin, HOMA, and ISI-composite.

RESULTS

Thirty-eight subjects completed the study protocol. The correlation coefficient between the ¹³C-GBT derived glucose-oxidized dose at 180 min and M values was 0.524 (p = 0.001). The optimal value to identify IR with the ¹³C-GBT was 4.23% (AUC 0.81; ₉₅CI 0.66, 0.96; accuracy 0.82, ₉₅CI 0.66, 0.92). The ¹³C-GBT sensitivity (0.88) was higher than HOMA and fasting insulin sensitivities (0.83 and 0.75 respectively), while their specificities were comparable (0.71, 0.71, and 0.79, respectively). The sensitivity of ISI-C was higher (0.92) than that of the ¹³C-GBT, but its specificity was poor (0.36). The accuracy of the ¹³C-GBT was superior to that of the other studied surrogates.

CONCLUSIONS

The ¹³C-GBT is a valid and accurate method to detect IR in non-diabetic adults. Therefore, it is potentially useful in clinical and community settings.

Sensitivity and specificity of cerebrospinal fluid glucose measurement by an amperometric glucometer

OBJECTIVES

To provide more data regarding the role of an amperometric glucometer in diagnosing meningitis. Methods: This is a prospective study conducted at the Pediatric and Neonatology Department, Qatif Central Hospital, Qatif, Saudi Arabia between March 2017 and September 2018. We measured glucose concentrations in cerebrospinal fluid (CSF) and blood using a central laboratory and amperometric glucometer (AG). We compared CSF/blood glucose ratios obtained in a central laboratory from clinical bedside examination with a glucometer, and calculated the sensitivity and specificity for detecting cases of meningitis. Results: A total of 101 patients with clinical suspicion of meningitis were recruited for CSF sampling. Of 101 CSF samples, 61 (60%) were suggestive of meningitis. Of 101 samples, 47 had hypoglycorrhachia identified by a standard laboratory, and 17% of them were also detected by AG. The correlation between CSF/blood glucose by AG and laboratory ratios was substantial (r=0.894, p  less than 0.01, 95% CI: 0.805-0.983). The AG sensitivity was 100% and specificity was 55% in pediatric cases, while in neonates the sensitivity was 86% and the specificity was 26%. Conclusion: Amperometric glucometers  can be used to detect hypoglycorrhachia accurately. This  point-of-care testing tool is easily accessible and can be used by health care providers for cases suspected of meningitis.

Analytical evaluation of HgbA1c, microalbumin, CRP, and RF on Architect ci8200 integrated system and workflow performance evaluation using computer simulation

BACKGROUND

Recently, hemoglobin A1c (HgbA1c), microalbumin (MA), C-reactive protein (CRP) and rheumatoid factor (RF) have been introduced on high throughput general chemistry system. We evaluated analytical performance of these assays on an integrated clinical chemistry and immunoassay analyzer and studied the impact of testing these assays on these systems on the overall efficiency of the analyzer, via computer simulation.

METHODS

The analytical performance was measured by determining precision, linearity and correlation of patient sample results with in-house testing methodology. MedModel simulation software is used to develop simulation model and process efficiency is determined by measuring turnaround times and resource utilization.

RESULTS

Between-days CVs ranged from 8.59% for MA to 3.22% for HgbA1c level 1 controls. Less than 2% carryover for all 4 methods was observed on the integrated analyzer. For HgbA1c on HPLC analyzer, the minimum and maximum TAT for a batch of 50 samples was 3.78 and 160 min, respectively, while for the integrated system it was 28.2 and 35.1 min, respectively. Labor utilization for the 2 processes ranged from 3.21% to 3.75%.

CONCLUSION

Chemistry module on an integrated system can be used to determine the HgbA1c and other serum proteins.

Proposed guidance for carryover studies, based on elementary equivalence testing techniques

BACKGROUND

Carryover experiments are widely used for clinical chemistry and immunochemistry analysers to evaluate and validate carryover effects. The experimental design is well described. However, there is no guideline on the statistical approach on data analysis, especially if absence of carryover has to be shown. The only reporting of carryover in ppm is not helpful because its uncertainty is not taken into account. Furthermore, the most commonly used method fails to demonstrate the absence of carryover. We propose a step-by-step guidance applying a new statistical design for analysis of carryover studies based on equivalence testing, and provide a sample based tutorial.

METHODS

For statistical analysis of carryover effects an one-sided version of equivalence testing by comparing the difference with a predefined limit (i.e., a test of non-superiority) is used. The methodology is demonstrated by measuring total betahCG in human serum samples with a UniCel DxI 880 analyser.

RESULTS

A new statistical approach based on equivalence testing has been developed for analysis of data resulting from a typical experimental protocol for carryover studies. Experiments using 8 (11) cycles of high and low concentration samples are appropriate to validate the absence of carryover with 80% (90%) power and an alpha-level of 0,05 if no carryover is expected. We propose to predefine an acceptance criterion based on the imprecision (here: expressed as one standard deviation) observed for those replicates of the low concentration samples expected to be unaffected by carryover. In the demonstration, the absence of carry-over was concluded with a significance of p < 0.05.

CONCLUSIONS

Appropriate statistical methods should be applied when the target of a method-validation experiment is (i) absence of any effect, (ii) non-inferiority/non-superiority or (iii) equivalence. Using the example of carryover studies, we show that one-sided equivalence testing is the proper model, and propose a guidance for analysis of these experiments. The example of carryover illustrates a methodology which is also applicable for analysis of a wide range of experimental approaches, including method comparison, commutability and robustness.

Amphetamines and 3,4-methylendioxymetamphetamine (MDMA): evaluation of KIMS (kinetic interaction of microparticles in solution) assay at two cut-off levels

Two screening methods for the assay of amphetamines and their derivatives have been applied to the same analytical instrument for their evaluation. In addition to an assay at a cut-off of 1000 μg/l, a new specific reagent was evaluated for an ultra-sensitive assay of amphetamines and 3,4-methylendioxyme-tamphetamine with a cut-off of 300 μg/l. The assay confirmation was performed using high-performance liquid chromatography and gas chromatography/mass spectrometry techniques. The results were positive for both screening methods, confirming the efficacy of two simultaneous methods with different cut-off levels.

Clinical biochemistry service for liver transplantation

The first significant successes with human liver transplantation took place only in 1968, but the future for this new surgical procedure now seems assured. Its success is heavily dependent upon the provision of pathology services, in particular from clinical biochemistry. The experiences with some of the 39 British liver transplants carried out so far are recorded. At operation, a minimum of 20 technician-hours, usually outside normal working hours, is called for. In the immediate post-operative period, intensive biochemical monitoring is essential. Once the major homeostatic mechanisms are re-established after surgery, the principal biochemical investigations are those of organ function. While no specific test for rejection is yet available, the diagnosis of rejection can be made from results of the routine pathology investigations. The role of the clinical biochemistry laboratory in the management of these patients is to provide reliable results seven days a week on a range of tests. The clinical biochemist is also well placed to contribute to the solution of some of the outstanding problems of organ transplantation.

[Non-specific reactions in four methods measuring (1-->3)-beta-D-glucan levels in plasma]

We detected non-specific reactions in the measurement of (1-->3)-beta-D-glucan levels (beta-glucan) in plasma, and the influences of the non-specific reactions on sensitivity and specificity of measurement methods were examined. In this study, 460 plasma samples from 174 patients at Kawasaki Medical School Hospital were used, and the plasma beta-glucan levels were measured by different four methods. The methods included the dilution-heating-endpoint (DHE), dilution-heating-turbidimetric (DHT), alkaline-kinetic (AK), and alkaline-endpoint method (AE) with and without 4-amidinophenyl benzoate hydrochloride (APB) of a protease inhibitor blocking the Limulus reaction. Non-specific reactions were detected from the calculated value under conditions with APB. Therefore, both of the actual values and the values equivalent to non-specific reactions were calculated. The incidence of non-specific reactions was 2.4% in DHE method, 0% in DHT, 53.3% in AK, and 99.3% in AE. The sensitivity and specificity in the methods were 35.7% and 96.0%, 28.6% and 96.0%, 78.6% and 80.1%, and 57.1% and 84.1%, respectively. When subtracted the non-specific reaction values from the actual values in AK and AE method, the specificity was increased by 91.4% and 94.0%, respectively. In these two methods, the non-specific reaction was considered to be a major cause of the low specificity. Finally, to measure plasma beta-glucan levels accurately, non-specific reactions should be excluded as possible by further improvement of measurement methods.

[Development of measurement methods and contributions to medical care in the clinical laboratory]

The level of professional interest in clinical chemistry shown by technologists tends to erode as the recent advances in automation of clinical laboratory tests have made it possible to obtain accurate data by simply using reagent kits. Therefore, the most of medical technologists have foolish preconceptions to be impossible for the development of the new measurement methods in the clinical laboratory. However, there should be many studies that medical technologist should perform. In this paper, I give an outline about practice of the chemical reagent development in the laboratory and the effect mainly on the HDL cholesterol (HDL-C) homogeneous method which we developed. Because homogenous methods can easily be performed by automated analyzers, they have been widely implemented not only in Japan, but also throughout the rest of the world. When compared to the precipitation methods requiring centrifugation, homogenous assays are superior because of the great savings in manpower, many more samples can be analyzed within a given time, smaller quantities of samples are required, assay times are shorter, and measurement accuracy is greater. The most important contribution of homogenous assays is that because measurement accuracy is higher, the degree of inter-laboratory differences has been markedly decreased, thus making it possible to establish international standards.

A quantitative in vitro assay for detecting biological activity of endotoxin using rabbit peripheral blood

The pyrogen test or the endotoxin test has been playing a crucial role in detecting endotoxin in parenteral drugs. The current test methods, however, have disadvantages such as requiring a relatively high number of animals or an inadequacy in direct evaluation of in vivo activity. We made an attempt to establish a new in vitro assay method that can overcome the shortcomings of the current assay methods. We standardized the system of tumor necrosis factor-alpha (TNF-alpha) induction from the peripheral blood of rabbits for assaying endotoxin activity. This in vitro assay showed a linear dose-response regression between 0.1 and 5.0 endotoxin units per milliliter of endotoxin and a definite homogeneity of variance by logarithmically transforming the endotoxin and TNF-alpha concentrations in the reaction mixtures at 5 h of incubation at 37 degrees C. The assay showed a definite correlation with the pyrogen test but not with the endotoxin test when endotoxins from various bacteria were tested.

Erratum: Sensitivity and specificity of cerebrospinal fluid glucose measurement by an amperometric glucometer

[No Abstract Available].

Complete blood count, clinical chemistry, and serology profile by using a single tube of whole blood from mice

Clinical pathology is a valuable means for assessing specific organ pathology and a screening tool for general animal health. Routine clinical pathology evaluation in mice usually includes whole blood for a complete blood count (CBC) and a clinical biochemistry analysis. Acquisition and analysis of these samples can be problematic due to the small volumes of blood that can be obtained from a mouse. Typically, a complete blood count requires blood from a tube containing an anticoagulant, whereas a clinical biochemistry profile needs blood from a serum clot tube. Because of the small volume that can be obtained, splitting the blood from a single mouse into 2 different tubes may result in inadequate samples to perform the desired tests or introduce inaccuracies. We explored the feasibility of using a single lithium heparin tube for generation of a CBC, biochemistry profile, and serology profile. We also evaluated the consistency of CBC data, including the quality of a peripheral blood smear taken from a lithium heparin or EDTA tube after various storage times. We found that CBC, biochemistry, and serology profiles could be obtained more readily when blood samples were placed in a single lithium heparin tube than in 2 separate tubes. In addition, the quality of blood smears and CBC results from the lithium heparin tube were comparable (with few exceptions) to those from an EDTA tube after prolonged storage.