Electrolytes internal quality control by using ISO 15189 version 2007: Particular requirements for quality and competence for biomedical laboratories

Background: the blood electrolytes analysis is a routine laboratory test which proper execution would help in the diagnosis of hydro-electrolytes disorders. The objective of this work was to assess the internal quality control of the sodium and potassium tests from the pre-pre-analytical phase to the post-analytical phase. Material and Methods: This was a cross-sectional study which took in the laboratory of biochemistry at the Institute of Cardiology, Abidjan, Ivory Coast from March 1st to March 31, 2009. We used the flame photometer to measure the sodium and potassium electrolytes level in the internal control Exatrol-Normal from Biolabo®. Clinical samples were also taken for the determination of the same electrolytes levels. The pre-pre-analytical quality indicators depending on the physicians order, the pre-analytical quality, the analytical quality and the post-analytical indicators under the control of the laboratory were assessed by using “NF en ISO 15189 version 2007” check list: Particular requirements for quality and competence for biomedical laboratories paragraph 5.4.1, 5.4.2, 5.5 and 5.7. Data were captured into Microsoft Excel [Microsoft Corporation, Redmond, WA] and then imported and analyzed using QI Macros SPC Software for Excel®. The levels of Na+ and K+ in the control material Exatrol Normal from Biolabo® were represented as follow: mean (m), Standard deviation (SD). The values of the monthly distribution of Na+ and K+ concentrations around the mean were used to draw the Levey-Jennings diagram and Wesgard’s rules were used to evaluate the performances of the analytical process. Results: a total of 112 electrolytes analysis order were received at the biochemistry laboratory. For the pre-pre-analytical phase, the analysis of these requests forms revealed that 81 (72.3%) requests forms carried no clinical information. The non-compliance of the samples were mainly represented by the sampling under tight tourniquet 4 (3.6%), followed by the non-respect of the succession of tubes during multiple sampling process 3 (2.7%). For the analytical phase, the monthly Levey-Jennings diagram showed a dispersion of the two electrolytes Exatrol-Normal Biolabo® levels ​​between the mean plus or minus 2 standard deviations [m ± 2SD]: 139.34 ± 2.84 mmol/L for Na+ and for K+, between [m± SD]: 4.2 ± 0.78 mmol/L. The analytical performances assessment for the two Levey-Jennings diagrams by using Wesgard’s rules did not found any significant critical deviations with regard to the distribution of Na+ and K+ levels. For clinical samples, isolated hyponatremia was the most common disturbance (30.4%) followed by isolated hypokalemia (12.5%). At the post-analytical phase we observed for test execution a mean turnaround time of 34 ± 5.2 minutes with extremes ranging from 23 to 95 minutes. One case (0.9%) of transcription error was noted. Conclusion: the internal quality control process is applied in the clinical biochemistry laboratory at the Institute of Cardiology, Abidjan. A systematic verification system of the different phases of the analytical process helped to follow quality indicators at all levels of the pre, analytical and post analytical process and corrective actions were taken if necessary. Better collaboration between clinicians requesting electrolytes analysis and biologists performing the analysis is necessary to improve the pre-pre-analytical phase and, beyond that, improve the patient outcome throughout a comprehensive care.