Serological Patterns of SARS-CoV-2 Infection and Their Association with Age, Sex, and Clinical Severity in Kirkuk, Iraq

Background: SARS-CoV-2 infection shows variable serological responses influenced by demographic and clinical factors, highlighting the importance of understanding antibody patterns across different patient groups. Aims of the study: This study aimed to evaluate SARS-CoV-2 serological patterns and determine their associations with age, sex, and clinical severity among individuals in Kirkuk, Iraq. Methodology: This study included 130 participants recruited from outpatient, inpatient, intensive, and respiratory care units at Kirkuk Medical City, Iraq, between August and December 2021. Demographic and clinical data were collected using a structured questionnaire. COVID-19 manifestations and severity were assessed by specialized physicians according to WHO criteria, incorporating symptoms, radiographic findings, and oxygen saturation. SARS-CoV-2-specific IgM and IgG antibodies were evaluated using serological immunoassays and the STANDARD Q COVID-19 IgM/IgG Duo Test, with antibody levels ≥10 AU/mL considered positive. Result: Among 130 participants, 41 (31.5%) had IgM-associated recent infection, 28 (21.5%) had IgG-associated previous infection, and 61 (46.9%) were seronegative. Females predominated in the IgM group (56.1%), whereas males predominated in the IgG group (71.4%). Mean age was higher in the IgM than IgG group (51.6 vs. 43.7 years). Most IgM-positive participants were ≥50 years (61.0%), while 75.0% of IgG-positive participants were aged 30–59 years. Among IgM-positive cases, 73.2% had moderate and 26.8% severe COVID-19. Conclusions: SARS-CoV-2 serological profiles varied according to age, sex, and clinical severity. IgM-associated recent infection was more frequent among older participants and females, while IgG-associated previous infection predominated among males and middle-aged individuals, highlighting distinct demographic and clinical patterns.