Use of reflex test in clinical biochemistry, determination of threshold values and cost analysis

Background and Aims: In today's medical practice, the use of laboratory test results in diagnostic decision-making greatly affects the clinical decision taken and directs clinicians to the source of the problem. With the increasing usability and accessibility based on technological developments, it is seen that some of the laboratory test requests, which are requested in increasing numbers every year, are requested inappropriately. In order to reduce unnecessary laboratory test requests, the importance of reflex and reflective test applications has been emphasized by the Ministry of Health within the scope of the Rational Laboratory Use Project and their use in laboratories has been encouraged. For this purpose, we aimed to determine the reflex test thresholds of the tests that are and are likely to be included within the scope of reflex test application in the literature and to show the cost benefits of reflex test application. Materials and Methods:The first 6 months of 2023 data of patients over the age of 18 who applied to Van Yüzüncü Yıl University Dursun Odabaş Medical Center polyclinics were included in the study. Reflex test algorithms and the most appropriate cut-off values to be used in reflex test applications were determined by ROC analysis and compared with the reference values used in our laboratory. Cost effectiveness and economic contribution were evaluated using reflex test numbers.We analyzed the results of 63148 patients in reflex TSH application. We found the lower and upper cut-off values determined by ROC analysis to be 0.282 and 6.77 μIU/mL. We found that with this reflex threshold we could save 80.7% of fT4 testing and miss 1.9% of fT4 testing. We calculated that 1,094,043 TL could be saved in terms of costs. Results:In TSH-sT4 reflex test application, the lower and upper cut-off values determined by ROC analysis of 63148 patient results were found to be 0.282 and 6.77 μIU/mL. It was found that with this reflex threshold, 80.7% of the fT4 test could be saved, and 1.9% of the time the fT4 test would be requested incompletely. In terms of cost (considering the latest supply prices in our hospital), it was found that 1,094,043 TL could be saved. The most appropriate cut-off value determined by ROC analysis of 15291 patient results in Reflex Bilirubin application was found to be 1.119 mg/dl. It was found that with this reflex threshold, unnecessary requests could be avoided 89.3% of the time, but requests could be missed 0.1% of the time. It was calculated that 86,026 TL could be saved in terms of costs. In the Reflex Icterus index application, the most appropriate cut-off value determined by ROC analysis of 17203 patient results was found to be 1.4 mg/dl. In the analysis performed for the threshold value of 0.8 mg/dl, it was found that 24% of the total bilirubin test could be saved and 0.1% of the total bilirubin test request could be missed. In terms of cost, it corresponds to 24,915 TL. In reflex ALT application, the most appropriate cut-off value determined by ROC analysis for 69091 patient results was found to be 25 U/L, 35 U/L and 30 U/L in female, male and total data, respectively. It was found that with the reflex threshold determined for the total data, 83.8% of the AST test could be saved and 0.8% of the AST test request could be missed. It was calculated that 364,845 TL could be saved in terms of costs. In reflex PSA application, it was calculated that with the reflex threshold determined for 2607 patient results (tPSA: 4-10 ng/ml), 34% of the sPSA test could be saved and 14,857 TL could be saved. According to the results of 3686 patients in the reflex test application we determined for TSH and Anti-TPO, it was calculated that 87.3% and 172,495 TL could be saved from the Anti-TPO test. We analyzed the results of 2216 patients in the reflex test application we determined for Anti-TPO and Anti-Tg requests and We found that we could save 16.3 percent on the Anti-Tg test. It was calculated that 21,400 TL could be saved in terms of cost. Discussion and Conclusion:Reflex test application constitutes a valuable step in preventing inappropriate requests towards rational laboratory use. By using the appropriate patient profile and cut-off values, many tests can be avoided without compromising patient safety. As demonstrated for the tests in this study, the reflex testing algorithms described increase time and cost effectiveness, which are the primary objectives of reflex testing. As laboratory professionals, interest in determining new reflex test algorithms and cut-off values for these and other tests continues to increase with increasing test diversity, time constraints and cost effectiveness. There is a need for further research, in which this study will lead to similar studies. Keywords: Reflex test, Reflective test, Rational laboratory use, Cost, Unnecessary test