Modeling of Platelet and Hematocrit in Dengue Hemorrhagic Fever (DHF) Patients Using Semiparametric Bi-response Regression Approach Based on Local Polynomial Estimator for Longitudinal Data

Dengue hematrocit fever (DHF) is a health problem in Indonesia, which tends to cause an increase in the number of sufferers and is becoming more widespread. Semarang City is an endemic region in Indonesia. Platelet and hematocrit modeling are required to diagnose DHF. The independent variables in this model were hemoglobin (Hb) level and examination time, whereas platelets and hematocrit were the dependent variables. This study used secondary data obtained from the Roemani Hospital in Semarang, Indonesia. The study included 13 patients who met the criteria for Grade 2 DHF, and their blood samples were collected once daily for 6 days during their hospitalization to form longitudinal data. This study aimed to model hematocrit and platelet counts using semiparametric bi-response regression with local polynomial estimators. The GCV method was used to select the optimal combination of bandwidth and polynomial order. The results obtained for platelets were a polynomial order of 2 and a bandwidth of 0.1, while hematocrit was selected with a polynomial order of 1 and a bandwidth of 0.8. Platelet and hematocrit modeling using the semiparametric bi-response regression applied to the in-sample data resulted in a coefficient of determination (R²) of 90.12%. The model results can be used to predict platelets and hematocrit with high accuracy, yielding an MAPE of 4.84%. Based on the analysis results, the increase in Hb and hematocrit has a unidirectional relationship (both increase) and is in the opposite direction to the number of platelets, which usually decreases (thrombocytopenia). Platelet dynamics in patients with Grade 2 DHF who were hospitalized for 6 days showed that on the 3rd or 4th day, the patient experienced thrombocytopenia and an increase in hematocrit above normal, which is a sign of plasma leakage; therefore, it is necessary to be aware that this patient's condition requires more intensive care to stabilize platelets and hematocrit.