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Effectiveness of thermal screening for COVID-19: Some considerations

Introduction: Fever is a common symptom in most infections, and its rapid identification forms a major component of screening efforts. Such screening has been carried out by several countries during the SARS outbreak in 2003 and during the influenza A (H1N1) 2009 pandemic. Materials and Methods: Infrared scanner-based non-contact (IRSBNC) thermometer was used to measure the forehead skin temperature. A conventional mercury thermometer was used to measure the core body temperature. Verbal informed consent was obtained from all the study subjects. Data collection was unlinked and anonymous, thereby maintaining privacy and confidentiality. A large sample size of 414 study subjects was taken. Data so collected were subject to appropriate statistical tests. The same data were utilized to run a simulation-based Susceptible Exposed Infected and Recovered (SEIR) model regarding the percentage of infectors likely to escape thermal screening and its epidemiological impact using MATLAB software. Results: The mean forehead skin temperature of the study subjects as measured by an IRSBNC thermometer was 96.79°F. The mean oral temperature of the study subjects as measured by a conventional mercury thermometer was 97.33°F. The difference between the two means was statistically significant with a t-value of 8.16 (P < 0.01). The forehead skin temperature as measured by an IRSBNC thermometer and oral temperature as measured by a conventional mercury thermometer showed a poor correlation coefficient of 0.11. Sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of IRSBNC thermometer work out to 0.5384, 0.7087, 0.1102, and 0.9581, respectively. The false positive rate is 0.2912; and the false negative rate is 0.0309. The values of sensitivity, specificity, positive predictive value, NPV, false positive rate, and false negative rate of IRSBNC thermometer estimated using standard statistical tests are not much different from the results obtained by the simulation-based model. Conclusion: Based on the previous literature available and on the findings of the present study, which have been further validated by running a simulation-based model, the workers recommend that not too much reliance be placed on thermal screening by the IRSBNC thermometer. IRSBNC thermometers are of limited utility in thermal screening for Covid-19.