Quality Control Assessment in the Clinical Chemistry Laboratory- A Ghanaian Study

Quality control is essential in the clinical laboratory in order to ensure reliability of results of tests, with acceptable levels of accuracy and precision. There is also the increasing awareness of the need for the exchange of accurate data between laboratories, whether for research and collaborative studies or for patient care. The objective of the study was to assess the level of quality control in the clinical chemistry laboratories in the Kumasi metropolis. Validation was made for 5 analytes (total cholesterol, urea, glucose, sodium and potassium). The study included determination of within-day (N = 20) and between-day imprecision (N = 20), inaccuracy (N = 20) and method comparison (with the acceptable WHO manual methods for each analyte and among the laboratories) for three laboratories KATH, Medilab and SDA using ethylene glycol stabilized bovine and human sera as well as pure analytes with known concentration. Structured questionnaires were also administered to assess the practice of quality control. For validation of complete analytical process total error (TE) was calculated. Results were assessed according to quality specification criteria given by European Working Group. Within-day imprecision CVs were all below 3% except for potassium from KATH and glucose from SDA (bovine serum). Between-day CVs for all analytes were below 9%, except for glucose (bovine serum) from SDA. Short-term (Within-day) performances as assessed with the capability index were all ≥1 except for urea from SDA with capability index < 1. However the autoanalysers were generally unstable in the long term with capability indices for most analytes recording a value less than 1. Inaccuracy was generally low but total error was high for most of the between-day results from the three laboratories which was due to the high imprecision. Total error assessment for cholesterol and urea measurement from both KATH and Medilab were acceptable per quality recommendation. Passing-Bablok regression analysis provided linear equation and 95% confidence interval for intercept and slope and this was used to assess analytical differences or agreement between the manual methods and the autoanalyzers. Complete accordance with WHO manual method was shown by total cholesterol, urea, sodium and potassium hence both methods can be used intercheangeably. However constant and proportional differences or both were shown by some results (glucose) from KATH, Medilab and SDA. A comparison of methods between the three laboratories showed a complete agreement between KATH and Medilab for all analtytes (with the exception of glucose for bovine serum). There were proportional differences between KATH and SDA for urea and glucose, whiles both constant and proportional differences were shown in results between Medilab and SDA. Financial constraints and knowledge of the use of control charts were among the major challenges laboratories faced in quality control practice. Analytes that do not fulfil quality specification criteria require more frequent quality control protocol which includes several runs of control material in series. Also since instrumental inexactness has been sighted as possible cause of errors, it is important that routine maintainance is carried out on the autoanalyzers. It is also essential that an oversight body is established that will regulate the continuous practice of method comparison studies in order to ensure between laboratory methods agreements.

Source: KNUST