Characterization Of Probable Causes Of Unacceptable Proficiency Testing Performance In Serum Urea.

BACKGROUND

Quality improvement in a modern clinical laboratory entails the continuous inspection and refinement of processes to ensure efficient and effective delivery of services that meet the needs and expectations of users. To measure effectiveness of the good laboratory practices put in place in a clinical laboratory, participation in proficiency testing (PT) is critical. However, participation alone may not guarantee improvement without thorough review of reports for elimination of unsatisfactory performance and prevention of all potential areas of PT failures. PT providers are required to provide an expert commentary on participants’ performance in regards to possible sources of error with reference to outliers and give suggestions for improvement as indicated in clause 4.7.2.2 of ISO 17043:2010 (General requirements for Proficiency testing). This study was carried out to compile and characterize those sources of errors in proficiency testing as gathered from the last four test events and further establish the frequency of occurrence for each error. Serum Urea was used as the indicator analyte because of its failure rate and utilization among participating laboratories. The participants evaluated used either Urease with Indicator Dye or Urease with GLDH methods and this would provide sufficient depiction for other analytes in basic chemistry that uses enzymatic method of analysis.

METHOD

Retrospective evaluation of basic chemistry reports released in 02/2018, 03/2018, 01/2019, 02/2019 test events was done. A total of 818 reports had been released, 711 being acceptable (Z-scores within +/- 2) and 107 unacceptable (Z-scores exceeding +/- 2). The unacceptable reports were investigated using Kaoru Ishikawa’s Fish bone diagram under the broad categories of Equipment, Personnel, Materials, Environment and Method. Troubleshooting was based on the Westgard rules and CLIA acceptability criteria for proficiency testing. Homogeneity and stability testing results in these four test events were all within the acceptable range with the samples standard deviations (ss) as 0.42, 0.33, 0.91 and 0.94 respectively (results in mmol/l) all ≤ 0.3 of the standard deviation of participants results.

RESULTS

CONCLUSION

Characterization of these errors and their frequencies will provide an opportunity for the continuous improvement by objectively informing laboratory management on corrective and preventive actions to put in place in mitigating PT failures. Similar actions as informed by this error’s profiling can also be taken against unacceptable performance in other analytes.