Preparation of in-house internal quality control material for the testing of hepatitis b surface antigen (HBSAG) in the medical microbiology laboratory, and an evaluation of its effectiveness

The primary duty of medical laboratories is to be able to give the patient reliable and accurate results. Every laboratory needs an internal quality control (IQC) program in order to do this. Using an IQC and control materials prevents potential errors being reflected in patients' results. The purpose of this study was to prepare in-house IQC materials in a laboratory environment using HBsAg-positive patient samples and to assess the efficacy of these materials under different storage conditions (at 4˚C, -20˚C and in lyophilized form). Prepared IQC materials were studied on 20 separate days using quantitative and qualitative kits in the form of one specimen a day, and the results were evaluated on a Levey-Jennings chart with Westgard rules. Study results within a ±2 standard deviation (SD) range were considered successful. Commercial IQC materials belonging to the kits were also included in the study. Twenty study results for in-house IQC materials stored at 4˚C were outside ±3SD. The storage of materials at 4˚C was therefore considered inappropriate. Nineteen of the 20 results for materials stored at -20˚C studied using a quantitative kit and 14 of the 20 results studied using a qualitative kit were within a ±2SD range. Ten of the 20 results for lyophilized materials studied with a quantitative kit and 7 of the 20 results studied with a qualitative kit were within a ±2SD range. All the results for IQC materials belonging to the kit were within a ±2SD range. In the second part of the study, up to 0.8% of the number of specimens arriving at the medical microbiology laboratory with a request for HBsAg analysis was divided into two and tested at different times, with one specimen being numbered during routine procedures and one being given an internal quality evaluation number. The aim in this study was to assess all the laboratory processes at HBsAg analysis. No difference capable of changing clinical diagnosis was observed among the results. In conclusion, results for in-house IQC materials stored at -20˚C are more reliable than those for materials stored at 4˚C and lyophilized forms. In addition, in-house IQC materials were not as stable as commercial IQC materials.