Exploring Blood Cell Count-Derived Ratios as Practical Diagnostic Tools for Scabies in Vulnerable Populations

Scabies is a neglected tropical disease and represents a considerable global burden. Although consensus diagnostic criteria for scabies have been recently published, diagnosing scabies infestation remains challenging in clinical practice. We investigated the diagnostic utility of complete blood cell count (CBC) and CBC-derived ratios obtained at diagnosis in a set of 167 patients who are Vietnamese with confirmed scabies. These parameters were compared with those of patients with dermatophytosis (N = 800) and urticaria (N = 2023), two diseases frequent in Vietnam, which can present with similar skin manifestations to scabies and tend to pose a diagnostic challenge in vulnerable populations. Our analysis revealed that white blood cell, monocyte, and eosinophil counts were significantly higher among patients with scabies than the other two diseases. Similarly, the monocyte-to-lymphocyte ratio (MLR) and eosinophil-to-lymphocyte ratio (ELR) were significantly higher among patients with scabies. The optimal cut-off values to distinguish scabies from dermatophytosis and urticaria were 0.094 for ELR (sensitivity: 74.85%, specificity: 70.7%) and 0.295 for MLR (sensitivity: 52.69%, specificity: 73.54%). CBC, ELR, and MLR are low-cost and easily calculated parameters that may be helpful for the diagnosis of scabies.