TABLE 2.
Results of prenatal rubella immunoglobulin G (IgG) testing in Alberta between August 1, 2002, and December 31, 2005
| Variable | Specimens, n | Seropositive | Seronegative | Indeterminate | P |
|---|---|---|---|---|---|
| Number of specimens, total | 140,444* | 127,800 (91.0) | 12,364 (8.8) | 280 (0.2) | – |
| Age, years | 139,798† | 28.1±5.6 | 24.4±5.8 | 25.5±5.6 | <0.0001 |
| Age category, years | <0.0001 | ||||
| <20 | 15,398 | 11,783 (76.5) | 3,566 (23.2) | 49 (0.3) | – |
| 20–24 | 26,380 | 22,579 (85.6) | 3,717 (14.1) | 84 (0.3) | – |
| 25–29 | 44,151 | 41,463 (93.9) | 2,606 (5.9) | 82 (0.2) | – |
| 30–34 | 36,119 | 34,547 (95.7) | 1,528 (4.2) | 44 (0.1) | – |
| 35–39 | 14,622 | 13,918 (95.2) | 689 (4.7) | 15 (0.1) | – |
| ≥40 | 3,128 | 2,933 (93.8) | 190 (6.1) | 5 (0.2) | – |
| Gravidity | 88,136† | 2.3±1.6 | 2.2±1.7 | 2.3±1.6 | <0.0001 |
| Parity | 84,027† | 1.0±1.2 | 0.8±1.3 | 1.0±1.3 | <0.0001 |
| Median rubella IgG titre, U/mL (IQR) | 140,440‡ | 56.9 (29.5–109.2) | 5.7 (2.5–7.9) | 12.4 (10.8–13.6) | <0.0001 |
| Health region | <0.0001 | ||||
| Calgary | 49,050 | 45,385 (92.5) | 3,580 (7.3) | 85 (0.2) | – |
| Edmonton | 41,039 | 37,697 (91.9) | 3,258 (7.9) | 84 (0.2) | – |
| Northern Alberta | 25,481 | 22,406 (87.9) | 3,023 (11.9) | 52 (0.2) | – |
| Southern Alberta | 24,874 | 22,312 (89.7) | 2,503 (10.1) | 59 (0.2) | – |
| Year | <0.0001 | ||||
| August – December 2002 | 15,247 | 13,990 (91.8) | 1,253 (8.2) | 4 (0.03) | – |
| 2003 | 40,097 | 36,852 (91.9) | 3,238 (8.1) | 7 (0.02) | – |
| 2004 | 41,377 | 37,827 (91.4) | 3,549 (8.6) | 1 (0.002) | – |
| 2005 | 43,723 | 39,131 (89.5) | 4,324 (9.9) | 268 (0.6)§ | – |
Data are represented as n (%) or mean ± SD.
Of the specimens that were not opted out of the rubella IgG screening (n=140,473), 29 had no result because of problems with testing (eg, insufficient blood sample);
Number of specimens of the 140,444 for which these data were recorded on the requisition;
Four specimens had an interpreted serological result (positive, negative or indeterminate), but the actual titre was not available;
The rise in the number of specimens having indeterminate serology in 2005 is due to a change in screening protocol that took effect as of December 1, 2005 (from this point onward, rubella IgG levels between 10 U/mL and 15 U/mL have been classified as indeterminate). IQR Interquartile range