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

Global efforts to manage the SARS-CoV-2 pandemic have relied heavily on rRT-PCR testing. However, this method requires specialized labs, trained personnel, and significant time. False-negative results and limited availability have hindered widespread testing. Prior research has shown that rRT-PCR remains the gold standard, but its limitations are well-documented. No prior work had resolved how routine blood tests might complement or replace rRT-PCR in resource-limited settings. That uncertainty drove the need to explore alternative diagnostic approaches. This gap motivated the investigation of hematological markers as potential indicators of SARS-CoV-2 infection. It was already known that blood parameters often change during viral infections. No prior work had resolved how these changes might specifically correlate with SARS-CoV-2. This gap motivated the study of plasma levels of WBCs, CRP, and liver enzymes in patients with suspected cases.

The study aimed to assess whether routine blood tests could serve as a diagnostic tool for SARS-CoV-2 infection. The specific problem addressed was the limitations of rRT-PCR testing, including delays, false negatives, and resource constraints. The motivation came from the urgent need for accessible diagnostic alternatives during the pandemic. This paper proposed to evaluate hematological and biochemical markers as potential indicators of infection. The researchers hypothesized that differences in these markers might distinguish positive and negative cases. The study sought to identify empirical thresholds for these parameters. No prior work had resolved how these thresholds might apply to SARS-CoV-2. This gap motivated the analysis of 207 patients with suspected cases.

The study analyzed plasma levels of WBCs, platelets, CRP, AST, ALT, GGT, alkaline phosphatase, and LDH in 207 patients. These patients were admitted to an emergency room in Milan with symptoms of SARS-CoV-2. All participants underwent rRT-PCR testing to confirm infection status. Of the 207 patients, 105 tested positive and 102 tested negative. The researchers compared the plasma levels between the two groups. They focused on identifying statistically significant differences in these markers. Empirical cutoffs were established for AST and LDH to classify patients. These thresholds were used to determine if routine blood tests could predict infection status.

The study found statistically significant differences in WBC, CRP, AST, ALT, and LDH levels between positive and negative patients. The most notable findings were observed in AST and LDH. Empirical thresholds for these enzymes allowed the identification of 70% of patients as either positive or negative. These thresholds were derived from the observed plasma levels in the study population. The results suggest that AST and LDH may serve as useful indicators of infection. The study did not find significant differences in platelet or GGT levels. Alkaline phosphatase showed no meaningful variation between groups. These findings propose that certain hematological parameters may help identify SARS-CoV-2 status.

The authors propose that combining appropriate cutoffs for specific hematological parameters could help identify false-positive or false-negative rRT-PCR results. They suggest that blood test analysis might serve as an alternative to rRT-PCR in resource-limited settings. This conclusion is based on the observed differences in AST and LDH levels. The study does not claim that these tests can replace rRT-PCR entirely. Instead, they may complement it in areas with limited access to PCR testing. The authors suggest that these findings may help improve diagnostic accuracy in such regions. They do not propose that these tests are essential for diagnosis. Rather, they may be useful in settings where PCR testing is unavailable.