Validation of a Clinical Risk-scoring Algorithm for Scrub Typhus Severity in South India

Abstract

A bstract Background A clinical risk-scoring algorithm (CRSA) to forecast the scrub typhus severity was developed from two general hospitals in Thailand where patients were classified into three groups—nonsevere, severe, and fatal. In this study, an attempt was made to validate the risk-scoring algorithm for prognostication of scrub typhus severity in India. Materials and methods This prospective study was conducted at a hospital in South India between November 2017 and March 2019. Patients of scrub typhus were categorized into nonsevere, severe, and fatal according to the CRSA. The patients were also grouped into severe and nonsevere according to the definition of severe scrub typhus which was used as a gold standard. The obtained CRSA score was validated against the classification based on the definition of severe scrub typhus. Receiver operating characteristics (ROC) curve for the scores was plotted and the Youden's index for optimal cutoff was used. Results A total of 198 confirmed cases of scrub typhus were included in the study. According to the ROC curve, at a severity score ≥7, an optimal combination of sensitivity of 75.9% and specificity of 77.5% was achieved. It correctly predicted 76.77% (152 of 198) of patients as severe, with an underestimation of 10.61% (21 patients) and an overestimation of 12.63% (25 patients). C onclusion In the present study setting, a cutoff of ≥7 for severity prediction provides an optimum combination of sensitivity and specificity. These findings need to be validated in further studies. How to cite this article Gulati S, Chunduru K, Madiyal M, Setia MS, Saravu K. Validation of a Clinical Risk-scoring Algorithm for Scrub Typhus Severity in South India. Indian J Crit Care Med 2021;25(5):551–556.

Scrub Typhus Diagnostics: The Present and the Future

“…The authors have reported an improved prediction of severity: approximately 77% of cases were correctly classified as severe [47]. An algorithm to differentiate scrub typhus from dengue has been described by Mitra et al, by using the variables of oxygen saturation, total white blood cell count, haemoglobin, total bilirubin, serum glutamic/ oxaloacetic transaminase (aspartate aminotransferase), and altered sensorium.…”

An Overview of the Clinical Profile and Risk Factors Associated with Severe Scrub Typhus Infection: A Hospital Based Study in Coimbatore

“…It is an acute zoonotic infection caused by a mite-borne bacterium called Orientia tsutsugamushi, which is transmitted via insect bites [3] . The arthropod responsible for this transmission, which also serves as a reservoir for this bacterium, is the Leptotrombidium mite [4][5][6][7][8] . O. tsutsugamushi is a Gram negative, obligate, intracellular organism [4,7] .…”

“…The incidence and clinical profile of ST have not been studied in depth in southern Indian states like Tamil Nadu. Clinically, ST manifests as high fever with malaise, headache, cough, myalgia, exanthematous rash, and lymphadenopathy along with the involvement of different systems, such as the respiratory, cardiovascular, and hepatobiliary systems as well as the brain [3,6,9] . This leads to manifestations like hepatitis, pneumonia, renal failure, septic shock, myocarditis, acute respiratory distress syndrome (ARDS), and multiple organ dysfunction syndrome (MODS) [3] .…”

“…A high case fatality rate close to 70% has been documented for untreated ST, while the mortality rate in treated cases is close to 1.4% [3,9] . Diagnosis of ST may be challenging as other tropical fevers which also tend to occur seasonally, such as dengue, malaria, typhoid, or leptospirosis, may overlap with ST clinical features [6] . Though the disease is endemic in Tamil Nadu state, limited studies are available regarding the clinical profile of ST. Also, as far as we know, no study has been conducted to analyze the disease pattern in the western and southern parts of the state.…”