Cycle threshold (Ct)values of SARS-CoV2 vary with the type of symptoms and comorbidities of the patients.

Background: Literature depicts no association of cycle threshold values for SARS-CoV-2 with the patient's demographics or clinical history. However, the severity of the COVID-19 symptoms showed some associations with Ct values in previous studies. We aimed to study the relationship of Ct values with type of the symptoms and comorbidities of the patients.

Methods And Results: We examined the individuals (n = 8660) that consulted a private diagnostic center for COVID-19 testing. Nasopharyngeal samples were collected from the patients and SARS-CoV-2 was detected by RT-PCR assays using Sansure Biotech kit. Clinical and demographic information was collected by the attending healthcare professional. The differences between groups were analyzed by t-test (unpaired). P-values < 0.05 were considered statistically significant. We found that the mean age of asymptomatic patients (41.47 ± 17.01 years) and symptomatic patients (47.75 ± 17.51) varies significantly (p value < 0.0001). Among the most prevalent symptoms were fever (77.74%) and cough (66.46%). The Ct values of COVID-19 patients with symptoms (25.70 for Orf1ab, 24.25 for N gene) were significantly lower than the Ct values of the patients without symptoms (28.99 for Orf1ab, 28.17 for N gene) (p value < 0.0001). Patients having co-occurrence of cough with fever (24.67 for Orf1ab, 22.86 for N gene) and solely fever (25.12 for Orf1ab, 24.01 for N gene) showed significantly lower Ct values than the patients without symptoms (28.99 for Orf1ab, 28.17 for N gene, p value < 0.0001). However, this difference was independent of patients sex and dependent upon patient's age and SARS-CoV-2 detected gene. The most prevalent comorbidities among COVID-19 patients were blood pressure (64.7%) and diabetes (50.5%). The patients having blood pressure and diabetes together showed significantly lower Ct values (23.37 for Orf1ab, 23.33 for N gene) than patients without comorbidities (27.65 for Orf1ab, 26.75 for N gene, p value < 0.001).

Conclusion: We conclude that the Ct values of the SARS-CoV-2 detected gene (either Orf1ab or N) is associated with the types of symptoms and comorbidities of the COVID-19 patients. Furthermore, the relationship between Ct values and symptomology or comorbidity of the patients is independent of patient's sex but dependent upon patient's age and SARS-CoV-2 detected gene.