Diagnostic model of visceral leishmaniasis based on bone marrow findings. Study of patients with clinical suspicion in which the parasite is not observed

Abstract Background Visceral Leishmaniasis (VL) is a serious protozoal disease endemic in diverse areas, including the southern area of Madrid (Spain), where an outbreak was detected in 2009. The objective of this work is to analyze bone marrow alterations in VL patients and elaborate a diagnostic model with the aim to improve the early detection of this disease. The usual diagnostic methods, as the observation of the parasite on a bone marrow aspirate, have frequent false negatives, and the high sensitivity methods, as PCR and ELISA, are delayed or are not always available. Methods This observational study evaluated bone marrow parameters of adult patients with clinical suspicion of VL, in which a bone marrow aspiration was performed but Leishmania was not directly observed, during the period 2009-2014. The patients finally diagnosed of VL by other methods (VL group, n=41), and the patients in which the VL was not diagnosed (non-VL group, n=20) were compared. A multivariant model was elaborated and externally validated. Results The final multivariant model includes percentage of myeloid series, percentage of plasma cells and quantification of megakaryocytes in the bone marrow, with an area under the ROC curve of 0.87 (0.78-0.96). The model performed well in the external validation. Conclusion In cases of VL suspicion and when the parasite is not observed in the bone marrow aspiration, the proposed model could be useful in discriminating between patients with and without VL, allowing to take a therapeutic decision while awaiting the definitive diagnosis.