Platelet to lymphocyte ratio in the healthy population of Vojvodina

The platelet-to-lymphocyte ratio (PLR) is a simple laboratory index that can be applied in the diagnosis and follow-up of various diseases, particularly those with a primary or accompanying systemic inflammatory component. However, its clinical utility is limited by the absence of established reference intervals in the general population. This study aimed to determine the reference interval for PLR.

This retrospective observational study included 4,672 adults who underwent regular systematic check-ups consisting of clinical examinations and basic laboratory analyses, including a complete blood count (CBC). The PLR reference interval was calculated using Clinical and Laboratory Standards Institute (CLSI) guidelines, which estimate percentiles and their 95% confidence intervals (CI). Verification of the reference interval was performed in a group of 95 healthy adults, matched by age and sex to the study cohort.

The mean age of participants was 43± 10 years, with a predominance of males (83.7% ). The median PLR was 109 (25th percentile: 90; 75th percentile: 131). The lower limit of the reference interval was 62 (95% CI: 61-63), and the upper limit was 194 (95% CI: 188-198). Female participants had significantly higher PLR values compared with males (P < 0.0001), while elderly participants had significantly lower PLR values compared with the middle-aged and younger groups (P= 0.019). The determined reference interval was 70-231 for females and 61-183 for males. PLR values did not differ significantly between the primary study group and the validation group [108.0 (87-136) vs. 109.0 (90-131); P> 0.05].

In this representative sample, consisting primarily of young and middle-aged adults, the PLR reference interval was 70-231 for women and 61-183 for men. In individuals older than 65 years, PLR values may be lower.