Production of low glucose serum for quality control and evaluation of yeast treatment, lyophilization and storage conditions on serum constituents

In order to provide quality control serum in the hypoglycemic range, pooled human serum was treated with yeast. Yeast destroyed about 50% of the serum glucose in about 4 1/2 hrs. The yeast-treated serum remained suitable for quality control of the most commonly analyzed clinical chemistry constituents which showed only very little change in most cases. Serum triglycerides were increased by about 40% and bilirubin decreased by about 20% during the treatment. Lyophilization of serum samples (yeast-treated or not) resulted in significant decreases of some enzymes activities. Exposure at 22 degrees C of samples lyophilized (7 days) and non-lyophilized (4 days) resulted in practically no change except for certain enzymes. No significant differences were observed in the clinical chemistry measurements including glucose one month and three months after preparation of samples lyophilized (stored in a refrigerator) and non-lyophilized (store in a freezer).

A scheme for the evaluation of methods in clinical chemistry with particular application to those measuring enzyme activities. Part I: general considerations

A 20-point system is presented whereby commercially produced clinical chemistry procedures, i.e., in vitro diagnostic kits, may be assessed for adequacy of packaging, labelling and enclosed literature. Criteria are given for the selection of a reference method to use in the test method evaluation and the design of a patient comparison study using these two methods is described. The importance of standards and calibration materials as they relate to accuracy and specificity is discussed. A procedure for assessing accuracy by recovery studies is outlined. A method for the assessment of precision on a within-day and a day-to-day basis is described.

A scheme for the evaluation of methods in clinical chemistry with particular application to those measuring enzyme activities. Part II: analysis of data and performance assessment

Recommendations are made concerning the editing of day-to-day reproducibility data for establishment of precision in the evaluation of a clinical chemistry method. The concept of diagnostic and equalized diagnostic indices is introduced together with formulae for their generation from the usual precision and accuracy data acquired in method evaluations. These indices allow direct comparison of data obtained from procedures for measuring enzyme activities which employ a variety of experimental conditions and units in their protocols. The equalized diagnostic index permits assessment of the suitability of the normal range assignment. Permissible limits of variation (PLV) and permissible limits of discrepancy (PLD) have been developed empirically from detailed examination of data from method evaluations and proficiency testing surveys in the published literature. The application of the diagnostic indices and the two permissible limits of criteria have been illustrated using data from the assessment of 19 kits measuring CPK activity. The inconsistency of the correlation coefficient in method comparisons is confirmed.

An investigation of factors influencing the measurement of creatine phosphokinase activity in serum using coupled enzymatic methods

1. The factors influencing the measurement of creatine phosphokinase (CPK) activity in serum by coupled enzymatic methods were investigated to establish optimum conditions for this type of assay. Such a study was indicated following observations by the authors of poor performance of commerically produced reagent kits together with the failure of most of the established an well accepted methods to operate under true optimum zero order kinetics in the reaction phase state. 2. The factors invested were the effects of pH, substrate concentrations (creatine phosphate, glucose and NADP+), added auxiliary (hexokinase) and indicator (glucose-6-phosphate dehydrogenase) enzymes, dithiothreitol (DTT) as an activator and conditions of storage of substrate stability. DTT was found to be a suitable activator but not a reactivator of the reaction. The optimum concentrations of creatine phosphate, glucose and NADP+ were found to be 20.0, 20.0 and 2.0 mmol/litre, respectively. Optimum activieies of the enzymes, glucose-6-phosphate dehydrosenase and hexokinase were 1000 and 2000 units/litre, respectively. 3. The between-day precision of the method for measuring serum at pH 6.8 and 30 degrees C at three activity levels under the optimum conditions developed was excellent yielding coefficients of variation ranging from 2.0 to 2.7%.

An evaluation of commercial kits for creatine phosphokinase assay

1. The evaluation of seven colorimetric and twelve kinetic or ultra-violet (UV) creatine phosphokinase (CPK) kit methods for their reliability as a diagnostic tool in clinical laboratories has revealed that over 35% of such commercial products readily available in Canada do not yield reliable results. 2. Six out of seven colorimetric kits failed to meet the criteria of minimum reliability as did one of the twelve UV kinetic kits.

The use of in vitro diagnostic kits in hospital laboratories in Canada

1. A survey conducted among hospital laboratories has yielded data from 640 institutions concerning the use of diagnostic kits and reagents in Canada. 2. Kits designed to test for chemical constituents were most frequently used in hospitals of 51 to 600 bed capacity whereas the ones for enzymes were most extensively used in 201 to 700 bed-size institutions. Kits based on the CPB principles were generally used in hospitals of more than 200 beds whereas those based on RIA were only in frequent use where the bed capacity was 351 or more. 3. The following tests were most often performed by kits: aminotransferases, amylase, urea, LDH, phosphatases, glucose, CPK, bilirubin, calcium, uric acid, T-4, T-3, digoxin and vitamin B12. 4. The survey reflects a continuing and increasing usage of in vitro diagnostic kits and associated blood analyzer systems. It also indicates a significant adoption of assay kits which utilize RIA and CPB principles.

Assessment of Two Blood-Analyzer Systems Intended for Diagnostic Testing in the Physician's Office

We have assessed the Bio-Dynamics "Unitest System" and the Dow Chemical "Diagnostest." Day-to-day reproducibility and within-day precision of the Unitest uric acid and urea nitrogen kits were beyond acceptable limits of error. For Diagnostest, day-to-day reproducibility of bilirubin was outside these limits for two concentrations of bilirubin, one each for uric acid and cholesterol. The Unitest kit gave falsely high readings for cholesterol such that incorrect diagnoses could result. The Diagnostest cholesterol procedure gave values significantly lower than those obtained with the AutoAnalyzer. With Unitest, low results were found on specimens with supranormal uric acid; with Diagnostest low results were obtained for supranormal concentrations of urea nitrogen. Both systems yielded acceptable results for glucose and hemoglobin. We conclude that personnel not technically trained could not obtain reliable data with these systems.

A survey of hemoglobin values in Canada

A compilation of hemoglobin values has been made from submissions from laboratories in Canada using the cyanmethemoglobin standard prepared and distributed by the Canadian Communicable Disease Centre (formerly the Laboratory of Hygiene). From 84 participating laboratories 21,580 values were analyzed statistically by age and sex. "Medical referrals", exclusive of blood dyscrasias, were included but were documented separately from "well persons". In most age groupings no significant difference in these two categories was found.Values for boys and girls were similar up to 12 years of age. For adult women from 18 to 84 years the mean value was 13.0 g. per 100 ml. (95% confidence limits 10.8-15.2 g.); for pregnant women 19 to 44 years the mean value was 12.2 g. per 100 ml. (9.7-14.6 g.). For men aged 17 to 24 years the mean value was 15.0 g. per 100 ml. (12.8-17.3 g.); 25-49 years 14.6 g. per 100 ml. (12.4-16.9 g.); 50-69 years 14.3 g. per 100 ml. (11.8-16.8 g.). It is noteworthy that for the most part the mean values were slightly lower than those frequently quoted as "normal" and that the mean values, particularly for the male, were lower with increasing age.