Platelet to Lymphocyte Ratio in Polymyositis as a Marker of Disease Activity.

BACKGROUND

Platelet to lymphocyte ratio (PLR) has been regarded as a parameter in assessing systemic inflammation. Polymyositis (PM) is a rare connective tissue diseases characterized by chronic muscle inflammation, which led to a hypothesis with respect to PLR in PM patients. Therefore, it is reasonable to investigate the relationship between PLR and PM.

METHODS

The present study included 46 newly diagnosed PM patients and 128 healthy subjects as controls. The muscle weakness of PM patients was measured using the manual muscle test (MMT) to evaluate disease activity in patients with PM.

RESULTS

Neutrophil to lymphocyte ratio (NLR) and PLR were higher in patients with PM compared with healthy controls (4.1 ± 1.32 vs. 1.6 ± 0.58, p < 0.001, 158.4 ± 86.39 vs. 103.8 ± 29.82, p < 0.001). PLR was positively correlated with NLR, ESR, and platelet counts (r = 0.392, p = 0.008, r = 0.422, p = 0.020, r = 0.366, p < 0.001), and negatively with lymphocyte counts (r = -0.872, p < 0.001) in patients with PM. Interesting, a reverse correlation between PLR and MMT score was observed in patients with PM (r = -0.383, p = 0.010). However, there was no correlation between NLR and MMT score (r = -0.266, p = 0.074). In logistic regression analysis, PLR was independently associated with PM after adjustment for age, gender, ESR, lymphocyte counts, neutrophil counts, leukocyte counts, and NLR. The resulting odds ratio (OR) and 95% confidence interval (95% CI) were 1.017 (95% CI 1.003 - 1.031; p = 0.015) for PLR.

CONCLUSIONS

Our research suggests that PLR is associated with PM, and PLR may be used to estimate disease activity of PM patients.