Perspective and consideration in the application of personalized reference intervals based on biological variation: a four-month observation of a woman with SARS-CoV-2 reinfection.

This study aimed to investigate potential benefit of personalized reference intervals (prRIs) by conducting a four-month observation of a woman with SARS-CoV-2 reinfection. Two types of prRIs were calculated: one derived from the population biological variation (BV) data provided by the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) biological variation database (prRIs__pop.), and the other derived from individual variation data (prRIs__ind.). These were subsequently compared. A total of 110 test results encompassing complete blood count (CBC) and leukocyte differential counts from the case were assessed according to the limits of prRIs__pop., reference change values (RCVs__pop.) and the population-based reference intervals (popRIs). In instances where limited historical health data are available (N ≤ 3), the application of prRIs__pop. was recommended over prRIs__ind. The prRIs__pop. and RCVs__pop. identified a greater number of potential clinical pathological change compared to popRIs (the ratio of potential abnormal values to total test values: prRIs__pop. 22/110, RCVs__pop. 25/110, popRIs 2/110, respectively). The findings suggest that the use of prRIs can be advantageous in clinical settings and is worthy of broader adoption. However, it is essential to choose an appropriate calculation method tailored to the specific clinical context.