Internal quality control of Na+ and K+ at clinical biochemistry laboratory

Abstract

Background: the blood electrolyte analysis is a routine laboratory test, the proper execution of which would help in the diagnosis of hydro-electrolyte disorders. We undertook to assess the quality of the sodium and potassium 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® and those of the clinical samples. The pre-pre-analytical quality indicators depending on the physician’s order, the pre-analytical quality indicators and the post-analytical indicators under the control of the laboratory and based on the NF standard ISO 15189 version 2012 have been determined. Data were captured into Microsoft Access [Microsoft Corporation, Redmond, WA] and then imported and analyzed using QI Macros SPC Software for Excel®. The monthly dispersion parameters of the Exatrol Normal were used to establish the Levey-Jennings diagram and the Wesgard’s rules were used for the interpretation. Results: a total of 112 electrolytes analysis order were received. For the pre-pre-analytical phase, the analysis of these requests revealed that 81 (72.3%) requests 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 tubes during multiple sampling 3 (2.7%). For the analytical phase, the monthly Levey-Jennings diagram showed a dispersion of the Exatrol-Normal® values ​​between the mean plus or minus 2 standard deviations [m ± 2SD]: 139.34 ± 2.84 mmol/L for sodium (Na+). For the potassium (K+), the values ​​of Exatrol-Normal® were between [m± SD]: 4.2±0.78 mmol/L. The interpretation of the two Levey-Jennings diagrams by Wesgard’s rules did not found any statistically significant mistake 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 a mean turnaround time of 34 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 makes it possible to identify errors at all levels of the analytical process and to take corrective action if necessary. Better collaboration between clinicians requesting electrolyte analysis and biologists performing the analysis is necessary to improve the pre-pre-analytical phase and, beyond that, better patient care.