Demographic data of probands with AS, their relatives and spouses by HLA-B27 status and presence of sacroiliitis by the modified New York criteria
| Number (%) | Men (%) | Women (%) | Mean age 1985 (SD) | |
| All participants | 1178 | 630 (53.5) | 548 (46.5) | 32.5 (10.3) |
| All AS probands | 363* | 249 (68.6) | 114 (31.4) | 44.2 (11.1) |
| HLA-B27 positive AS probands | 308/358 (86.0) | 219 (71.1) | 89 (28.9) | 44.0 (11.1) |
| Sacroiliitis present | 247/305 (81.0) | 185 (74.9) | 62 (25.1) | 44.6 (11.6) |
| Sacroiliitis absent | 58/305 (19.0) | 32 (55.2) | 26 (44.8) | 41.7 (8.5) |
| Pelvic X-ray not available | 3/308 (1.0) | 2 (66.7) | 1 (33.3) | 40.3 |
| HLA-B27 negative AS probands | 50/358(14.0) | 26 (52.0) | 24 (48.0) | 46.1 (11.5) |
| Sacroiliitis present | 22/50 (44.0) | 16 (72.7) | 6 (27.3) | 46.9 (10.1) |
| Sacroiliitis absent | 28/50 (56.0) | 10 (35.7) | 18 (64.3) | 45.6 (12.7) |
| All relatives | 806 | 380 (47.1) | 426 (52.9) | 27.1 (8.0) |
| Relatives of HLA-B27 positive probands | 672† | 311 (46.3) | 361 (53.7) | 26.9 (8.2) |
| HLA-B27 positive relatives | 360/668 (53.9) | 159 (44.2) | 201 (55.8) | 26.6 (8.1) |
| Sacroiliitis present | 14/308 (4.5) | 7 (50.0) | 7 (50.0) | 33.5 (4.1) |
| Sacroiliitis absent | 294/308 (95.5) | 128 (43.5) | 166 (56.5) | 28.4 (7.4) |
| No pelvic X-ray (age <18 year or pregnant) | 52/360 (14.4) | 24 (46.2) | 28 (53.8) | 14.7 (3.3) |
| HLA-B27 negative relatives | 308/668 (46.1) | 149 (48.4) | 159 (51.6) | 27.1 (8.4) |
| Sacroiliitis present | 0/278 (0) | |||
| Sacroiliitis absent | 278/278 (100) | 133 (47.8) | 145 (52.2) | 28.3 (8.1) |
| No pelvic X-ray (age <18 year or pregnant) | 30/308 (9.7) | 16 (53.3) | 14 (46.7) | 16.0 (4.4) |
| Relatives of HLA-B27 negative probands | 94‡ | 53 (56.4) | 41 (43.6) | 26.1 (6.6) |
| HLA-B27 positive relatives | 3/92 (3.3) | 2 (66.7) | 1 (33.3) | 22.0 |
| Sacroiliitis absent | 2/2 (100) | 1 (50.0) | 1 (50.0) | 26.5 |
| No pelvic X-ray (age <18 year) | 1/3 (33.3) | 1 (100) | 0 (0) | 13.0 |
| HLA-B27 negative relatives | 89/92 (96.7) | 49 (55.1) | 40 (45.9) | 26.4 (6.5) |
| Sacroiliitis absent | 83/83 (100) | 45 (54.2) | 38 (45.8) | 27.4 (6.0) |
| No pelvic X-ray (age <18 year) | 6/89 (6.7) | 4 (66.7) | 2 (33.3) | 12.7 (1.0) |
| Relatives of probands HLA-B27 unknown | 40§ | 16 (40.0) | 24 (60.0) | 33.5 (5.2) |
| HLA-B27 positive relatives | 15/39 (38.5) | 8 (53.3) | 7 (46.7) | 34.7 (5.0) |
| Sacroiliitis absent | 14/14 (100) | 8 (57.1) | 6 (42.9) | 34.9 (5.2) |
| No pelvic X-ray (pregnant) | 1/15 (6.7) | 0 | 1 (100) | 32.0 |
| HLA-B27 negative relatives | 24/39 (61.5) | 8 (33.3) | 16 (66.7) | 32.5 (5.3) |
| Sacroiliitis absent | 22/22 (100) | 8 (36.4) | 14 (63.6) | 32.6 (5.4) |
| No pelvic X-ray (pregnant) | 2/24 (8.3) | 0 | 2 (100) | 31.5 |
| Spouses | 9¶ | 1 (11.1) | 8 (88.9) | 47.7 (4.7) |
| HLA-B27 negative spouses | 9/9 (100) | 1 (11.1) | 8 (88.9) | 47.7 (4.7) |
| Sacroiliitis absent | 8/8 (100) | 1 (12.5) | 7 (87.5) | 48.4 (4.6) |
Total number of pelvic radiographs 1081 (probands 360; relatives 713, spouses 8).
*HLA-B27 status unknown for five probands, including one without sacroiliitis by New York criteria.
†HLA-B27 status of four relatives unknown (no sacroiliitis: three; pelvic radiograph not available: one).
‡HLA-B27 status of two relatives unknown (both did not show sacroiliitis).
§HLA-B27 status of one relative unknown (no sacroiliitis).
¶No pelvic radiograph available for one spouse.
AS, ankylosing spondylitis.