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Diagnosis of COVID-19 by Serology in Admitted Patients with Negative RT-PCR Assay
Mitra Rezaei1, Parvaneh Baghaei2, Makan Sadr3
1Virology Research Center, National Research Institute of Tuberculosis and Lung diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran. M.rezaie@sbmu.ac.ir.
Insights
For diagnosing COVID-19, serological tests are valuable additions to reverse transcription-polymerase chain reaction (RT-PCR) when initial tests are negative. Combining both methods significantly improves the detection rate of active coronavirus disease 2019 cases.
Area of Science:
- Infectious Diseases
- Virology
- Diagnostic Medicine
Background:
- The high prevalence of COVID-19 necessitates accurate diagnostic methods.
- False-negative results from initial reverse transcription-polymerase chain reaction (RT-PCR) tests pose a challenge in diagnosing active coronavirus disease 2019 (COVID-19).
- There is a need for complementary diagnostic approaches to improve COVID-19 case detection.
Purpose of the Study:
- To evaluate the diagnostic utility of serological tests as an adjunct to RT-PCR in patients with suspected COVID-19 and negative initial PCR results.
- To compare the diagnostic yield of repeat RT-PCR and serological testing (IgM and IgG antibodies).
- To determine the optimal timing for serological testing in relation to symptom onset.
Main Methods:
- A prospective study involving 137 patients with clinical and radiological signs suggestive of COVID-19 but negative initial RT-PCR tests.
- Second RT-PCR testing and serological evaluation for anti-COVID-19 IgM and IgG antibodies were performed.
- Results from repeat RT-PCR and serology were compared with each other and with clinical suspicion.
Main Results:
- Repeat RT-PCR was positive in 32.8% of patients.
- Anti-COVID-19 IgM and IgG antibodies were detected in 60.6% and 62.8% of patients, respectively.
- Serological testing alone was diagnostic in 73% of cases, with higher sensitivity after the first week of illness (88% vs. 54.8%).
Conclusions:
- Serological tests are effective complementary tools for diagnosing COVID-19, particularly when initial RT-PCR results are negative.
- Combining serological tests with RT-PCR enhances the overall diagnostic yield, achieving 83.9% case detection.
- Serology demonstrates significant diagnostic value, especially after the initial week of symptoms, aiding in the management of admitted symptomatic COVID-19 cases.
Abstract:
Considering the increasing prevalence and burden of coronavirus disease 2019 (COVID-19) disease and false-negative results in routine reverse transcription-polymerase chain reaction (RT-PCR) tests, additional diagnostic methods are needed to diagnose active cases of this disease. This prospective study was conducted on patients, in whom clinical and radiological symptoms/signs were in favor of COVID-19 while their first PCR test was negative. Later on, a second RT-PCR was performed and serological evaluation was carried out and results were compared with each other. Out of 707 patients who had been referred to the hospital and were clinically and radiologically suspicious of disease, 137 patients with negative RT-PCR tests entered the study. RT-PCR assay became positive for the second time in 45 (32.8%). Anti-COVID-19 IgM and IgG antibodies were positive in 83 (60.6%) and 86 (62.8%) patients, respectively. Finally, it was determined that serological test was diagnostic in 73% of patients and the diagnostic yield of serology was significantly higher after the first week of illness (54.8% in the first week and 88% after that). Taking advantage of both serological tests and RT-PCR helps in diagnosing 83.9% of cases. Based on the present study, the serology may be useful as a complementary test and in parallel to RT-PCR assay for diagnosis of COVID-19 among admitted symptomatic cases.
