Changes in neutrophil-to-lymphocyte and monocyte-to-lymphocyte ratios after multidrug therapy in multibacillary leprosy

To the Editor, Multibacillary leprosy is characterized by a high bacillary load and complex immune responses, with systemic inflammation playing a central role in disease progression and the development of reactional states.[1,2] Simple hematological indices derived from routine blood counts, such as the neutrophil-to-lymphocyte ratio (NLR) and monocyte-to-lymphocyte ratio (MLR),[3,4] are increasingly used as surrogate markers of inflammatory burden in various infectious and immune-mediated diseases, including leprosy.[3,5] While previous studies have primarily focused on the role of these ratios in predicting leprosy reactions,[5,6] data regarding their longitudinal behaviour following multidrug therapy (MDT) remain limited. In this correspondence, we report exploratory observations regarding the changes in the NLR and MLR before and after MDT in patients with multibacillary leprosy. This study was approved by the Health Research Ethics Committee of the Faculty of Medicine and Health Sciences, Universitas Muhammadiyah Makassar (519/UM.PKE/II/45/2024) and was conducted in accordance with the Declaration of Helsinki. The requirement for individual informed consent was waived by the ethics committee due to the retrospective design of the study and the use of anonymised medical record data. This retrospective cohort study involved 40 adult patients with newly diagnosed multibacillary leprosy treated at a referral dermatology center in South Sulawesi, Indonesia, between February and October 2024. All participants were free of acute leprosy reactions at baseline and were re-evaluated at release from treatment (RFT). Baseline hematological parameters were obtained from medical records prior to MDT initiation, and follow-up blood samples were collected 2–3 weeks after RFT. Neutrophil, lymphocyte, and monocyte counts were measured using an automated hematology analyzer to calculate the NLR and MLR. During follow-up, patients were categorized descriptively into three groups: those without a reaction, those who developed a type 1 reaction (reversal reaction, T1R), and those who developed a type 2 reaction (erythema nodosum leprosum, ENL). Overall, both NLR and MLR consistently decreased following MDT completion across all patient subgroups. For example, in patients without reaction, the median NLR declined from approximately 14 at baseline to about 2, with a similarly marked reduction observed in the MLR (Table 1). Comparable downward trends were observed among patients who developed T1R or ENL during follow-up. These findings indicate a general reduction in systemic inflammation following MDT, regardless of reactional status. Given the correspondence format, the results are presented descriptively to highlight observed longitudinal patterns rather than to infer diagnostic or predictive performance. Table 1 - Changes in neutrophil-to-lymphocyte ratio (NLR) and monocyte-to-lymphocyte ratio (MLR) before and after multidrug therapy (MDT) Variable Without reaction group (n = 18) Type 1 reaction group (n = 7) Type 2 reaction group (n = 15) NLR Before MDT 14.52 (12.64–15.67) 16.00 (13.06–17.33) 15.10 (12.54–23.55) After MDT 1.98 (1.72–3.38) 3.64 (2.84–5.56) 3.13 (2.09–3.56) P