The use of routine blood tests to assist the diagnosis of COVID-19 in symptomatic hospitalised patients.

IntroductionSpecific patterns of blood test results are associated with COVID-19 infection. The aim of this study was to identify which blood tests could be used to assist in diagnosing COVID-19. MethodA retrospective review was performed of consecutive patients referred to hospital with a clinical suspicion of COVID-19 over a period of 4 weeks. The patientâs clinical presentation, and SARS-CoV-2 RT-PCR (reverse-transcription polymerase chain reaction) were recorded. The patients were divided by diagnosis into COVID (COVID-19 infection) or CONTROL (an alternate diagnosis). A retrospective review of consecutive patients over a further 2-week period were used for the purposes of validation. ResultsOverall, 399 patients (53% COVID, 47% CONTROL) were analysed. White cell count (WCC), neutrophils (NEU) and lymphocytes (LYM) were significantly lower, while lactate dehydrogenase (LDH) and ferritin (FER) were significantly higher, in the COVID group in comparison to CONTROL. Combining the WCC, LYM and FER results into a COVID Combined Blood Test (CCBT) had an AUC of 0.79. Using a threshold CCBT of -0.8 resulted in a sensitivity of 0.85 and a specificity of 0.63. Analysing this against a further retrospective review of 181 suspected COVID-19 patients, using the same CCBT threshold, resulted in a sensitivity of 0.73 and a specificity of 0.75. The sensitivity was comparable to the SARS-CoV-2 RT PCR. DiscussionMathematically combining the blood tests has the potential to assist clinical acumen allowing for rapid streaming and more accurate patient flow pending definitive diagnosis. This may be of particular use in low resource settings.