Assessment of the utility of a screening tool for COVID-19 diagnosis in an accident and emergency department in Lagos, Nigeria: A pilot study

Abstract

The use of reverse transcription–polymerase chain reaction (RT-PCR) is the gold standard laboratory test for diagnosing SARS-CoV-2 infection. However, it has the disadvantage of a long turnaround time and cost. The Nigeria Centre for Disease Control (NCDC) formulated a case definition for COVID-19. We sought to determine the utility of a 14-item, point-weighted clinical screening questionnaire adapted from the NCDC case definition in identifying patients more likely to have the disease. This was to aid prompt clinical decision-making. Methods: We retrospectively reviewed the data of 113 non-surgical patients presenting to the Accident and Emergency Department (A and E) of Lagos University Teaching Hospital, Lagos, Nigeria. Patients were stratified based on screening scores into low (0–2), moderate (3–5) and high (6) pre-test categories. Patients with low and high scores ≥6 were admitted to the A and E and the COVID-19 holding ward, respectively, while the moderate group had chest computed tomography scans to aid further decision-making, pending the outcome of their RT-PCR results. The validity of the triage score as compared to the RT-PCR test result was calculated and the kappa score of agreement was utilised to evaluate the concordance between two triage scores. The optimum cut-off score was also obtained based on the maximal Younden's index. Results: The frequencies of low, moderate and high pre-test scores were 34 (30%), 43 (38.1%) and 36 (31.9%), respectively. Overall, 38.1% (43/113) were RT-PCR positive. RT-PCR was positive in 26.5% (9/34) with low screening scores, 55.8% (24/43) with moderate scores and 27.8% (10/36) with high scores. The sensitivity and specificity of a high score of 6 were 25% and 92.86%, while the lower score of 3 had sensitivity and specificity of 62.5% and 58.6%, respectively. Conclusion: The screening tool showed a high specificity in its initial design, which suggests that anyone with a low score using this tool has a high probability of testing negative. We recommend a cut-off score of 4 (score A) or 6 (score B) of the current screening tool be used to increase the chances of identifying persons with COVID-19 for RT-PCR testing.

Keywords

• accident and emergency
• covid-19
• reverse transcription–polymerase chain reaction
• screening tool