Table 2.
Associations of antibody titers (optical densities) higher than the median value (≥27.0) among the 18,844 antibody-positive individuals
| Characteristics | Tested |
Higher antibody titers than the median |
Univariable regression analysis |
F Test |
Multivariable regression analysis |
|||
|---|---|---|---|---|---|---|---|---|
| N (%) | N (%a) | p value | ORa (95% CI) | p value | p valueb | AORa (95% CI) | p valuec | |
| Sex | ||||||||
| Women | 4,387 (23.3) | 2,175 (52.1) | 0.702 | 1.00 | 0.702 | – | – | |
| Men | 14,457 (76.7) | 7,244 (51.6) | 0.98 (0.88–1.09) | 0.702 | – | – | ||
| Age (years) | ||||||||
| 20–29d | 2,867 (15.2) | 1,360 (47.6) | <0.001 | 1.00 | <0.001 | 1.00 | ||
| <10 | 243 (1.3) | 170 (70.0) | 2.57 (1.92–3.45) | <0.001 | 2.85 (2.12–3.83) | <0.001 | ||
| 10–19 | 407 (2.2) | 210 (54.0) | 1.30 (1.02–1.65) | 0.036 | 1.19 (0.90–1.56) | 0.220 | ||
| 30–39 | 5,533 (29.4) | 2,701 (48.1) | 1.02 (0.92–1.13) | 0.692 | 0.98 (0.88–1.09) | 0.678 | ||
| 40–49 | 4,876 (25.9) | 2,442 (50.1) | 1.11 (1.00–1.22) | 0.051 | 1.13 (1.02–1.26) | 0.025 | ||
| 50–59 | 3,220 (17.1) | 1,634 (50.8) | 1.14 (1.02–1.27) | 0.020 | 1.20 (1.07–1.35) | 0.002 | ||
| 60–69 | 1,281 (6.8) | 700 (54.2) | 1.31 (1.14–1.50) | <0.001 | 1.46 (1.26–1.70) | <0.001 | ||
| 70–79 | 315 (1.7) | 158 (49.7) | 1.09 (0.86–1.38) | 0.480 | 1.38 (1.07–1.77) | 0.012 | ||
| 80+ | 102 (0.5) | 44 (41.7) | 0.79 (0.52–1.19) | 0.254 | 1.27 (0.82–1.97) | 0.281 | ||
| Nationality | ||||||||
| All other nationalitiese | 2,203 (11.7) | 1,064 (51.7) | <0.001 | 1.00 | <0.001 | 1.00 | ||
| Bangladeshi | 3,471 (18.4) | 1,946 (56.2) | 1.20 (1.04–1.38) | 0.012 | 1.68 (1.45–1.94) | <0.001 | ||
| Nepalese | 2,236 (11.9) | 1,099 (49.3) | 0.91 (0.78–1.06) | 0.210 | 1.54 (1.32–1.80) | <0.001 | ||
| Filipino | 1,100 (5.8) | 507 (46.2) | 0.80 (0.65–0.99) | 0.038 | 1.30 (1.05–1.61) | 0.017 | ||
| Indian | 4,114 (21.8) | 2,027 (51.0) | 0.97 (0.84–1.13) | 0.699 | 1.22 (1.05–1.43) | 0.011 | ||
| Pakistani | 1,419 (7.5) | 731 (55.5) | 1.16 (0.96–1.41) | 0.124 | 1.19 (0.98–1.44) | 0.076 | ||
| Sri Lankan | 556 (3.0) | 242 (45.2) | 0.77 (0.59–0.99) | 0.044 | 1.12 (0.87–1.44) | 0.392 | ||
| Sudanese | 466 (2.5) | 264 (53.2) | 1.06 (0.78–1.44) | 0.712 | 1.04 (0.77–1.41) | 0.789 | ||
| Egyptian | 1,150 (6.1) | 535 (49.0) | 0.90 (0.73–1.10) | 0.283 | 0.82 (0.67–1.01) | 0.062 | ||
| Qatari | 2,129 (11.3) | 1,004 (51.8) | 1.00 (0.84–1.21) | 0.959 | 0.78 (0.65–0.94) | 0.010 | ||
| Clinical care encounter type | ||||||||
| Emergency | 3,333 (17.7) | 1,866 (58.5) | <0.001 | 1.00 | <0.001 | 1.00 | ||
| Outpatient | 5,264 (27.9) | 3,189 (60.7) | 1.10 (0.97–1.25) | 0.136 | 1.06 (0.94–1.21) | 0.334 | ||
| Home care/follow-up consultations | 3,939 (20.9) | 2,195 (58.3) | 0.99 (0.86–1.14) | 0.915 | 1.00 (0.87–1.15) | 0.987 | ||
| Inpatient | 6,308 (33.5) | 2,169 (35.2) | 0.39 (0.34–0.44) | <0.001 | 0.38 (0.34–0.43) | <0.001 | ||
| Antibody test date | ||||||||
| Calendar date (a linear term) | 18,844 (100.0) | 9,419 (51.8) | <0.001 | 1.014 (1.012–1.016) | <0.001 | <0.001 | 1.011 (1.010–1.013) | <0.001 |
AOR, adjusted odds ratio; CI, confidence interval; OR, odds ratio.
Estimates are proportions of persons with antibody titers higher than the median among those antibody-positive, weighted by sex, age, and nationality.
Covariates with p value ≤0.2 in the univariable analysis were included in the multivariable analysis.
Covariates with p value ≤0.05 in the multivariable analysis were considered strong predictors of anti-SARS-CoV-2 positivity after adjustment for age, nationality, clinical care encounter type, and antibody test date.
The 20–29 age group was chosen as the reference group (instead of the <10 age group) because of the larger sample size and for epidemiological relevance.
These include other nationalities residing in Qatar.