A comparative study of laboratory findings in PCR-positive and PCR-negative COVID-19 hospitalized patients

INTRODUCTION: Given the many misconceptions in terms of both diagnosis and treatment, SARS-CoV-2 continues to infect and victimize. Notwithstanding molecular testing is the gold standard method of in vitro diagnostic, the often long-waiting time, as well as false-negative results are daunting challenges facing us. In this study, we aimed to report the diagnostic value of laboratory findings in COVID-19 patients, with an extensive focus on the differences between PCR-positive and PCR-negative cases. PATIENTS AND METHODS: We did a retrospective single-centre study on a large cohort of 1546 COVID-19 patients in Tehran, Iran. Based on clinical symptoms, chest CTs were performed for all the patients. Also, molecular testing of swab specimens was also performed for 1450 cases. RESULTS: All the data on laboratory results were retrospectively extracted from medical records. Of the 1546 patients, 1040 (67.5%) were male and 506 (32.5%) were female with the mean age of 55.67. On admission, 31.4% of the whole study population displayed lymphopenia and 38.9% showed neutrophilia. Decreased hemoglobin and mild thrombocytopenia were also found in 40% and 18.6% of cases, respectively. Elevated lactate dehydrogenase in nearly 75% of COVID-19 cases was the most common alteration amongst biochemical parameters which together with increased ESR and CRP could serve as diagnostic markers in SARS-CoV-2 infection. Of the 1450 patients with a PCR result, 439 (28.3%) were PCR-negative and 1011 (65.3%) were PCR-positive. Notably, lymphopenia and increased AST were higher in the PCR-positive group than their negative counterparts. Albeit being in the normal range, a significant decrease in the number of monocytes was also evident in the PCR-positive cases. CONCLUSIONS: As far we are aware, this is the first time that we reported a comprehensive exploration of laboratory characteristics of a large cohort of hospitalized COVID-19 patients from Iran, hoping that these data will cast more light on the diagnostic significance of these parameters.