Routine blood tests as a potential diagnostic tool for COVID-19

TLDR

The SARS‑CoV‑2 pandemic has spread worldwide, and while rRT‑PCR is the gold standard for diagnosis, it is slow, costly, and prone to false negatives, limiting its use to symptomatic patients. The study aims to evaluate whether routine blood tests can serve as a cheaper, more accessible alternative diagnostic tool for COVID‑19. Researchers measured routine hematological and biochemical markers (WBC, platelets, CRP, AST, ALT, GGT, ALP, LDH) in 207 emergency‑room patients and compared the results with rRT‑PCR outcomes. Significant differences were found in WBC, CRP, AST, ALT, and LDH, and thresholds for AST and LDH correctly classified about 70 % of patients, suggesting that blood‑test cutoffs could help detect false‑positive/negative rRT‑PCR results and serve as an alternative diagnostic approach in resource‑limited settings.

Abstract

Abstract Objectives The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to date, the epidemic has gradually spread to 209 countries worldwide with more than 1.5 million infected people and 100,000 deaths. Amplification of viral RNA by rRT-PCR serves as the gold standard for confirmation of infection, yet it needs a long turnaround time (3–4 h to generate results) and shows false-negative rates as large as 15%–20%. In addition, the need of certified laboratories, expensive equipment and trained personnel led many countries to limit the rRT-PCR tests only to individuals with pronounced respiratory syndrome symptoms. Thus, there is a need for alternative, less expensive and more accessible tests. Methods We analyzed the plasma levels of white blood cells (WBCs), platelets, C-reactive protein (CRP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyl transpeptidase (GGT), alkaline phosphatase and lactate dehydrogenase (LDH) of 207 patients who, after being admitted to the emergency room of the San Raffaele Hospital (Milan, Italy) with COVID-19 symptoms, were rRT-PCR tested. Of them, 105 tested positive, whereas 102 tested negative. Results Statistically significant differences were observed for WBC, CRP, AST, ALT and LDH. Empirical thresholds for AST and LDH allowed the identification of 70% of either COVID-19-positive or -negative patients on the basis of routine blood test results. Conclusions Combining appropriate cutoffs for certain hematological parameters could help in identifying false-positive/negative rRT-PCR tests. Blood test analysis might be used as an alternative to rRT-PCR for identifying COVID-19-positive patients in those countries which suffer from a large shortage of rRT-PCR reagents and/or specialized laboratory.