Table 3.
Autoantibody positivity, levels of various autoantibodies in positive samples and number of positive autoantibodies in familial groups and in the sporadic group at diagnosis of type 1 diabetes
| Autoantibodies | n | 1. Affected father, n=253 (5.1%) | 2. Affected mother, n=141 (2.8%) | 3. Affected sibling, n=95 (1.9%) | 4. ≥2 affected family members, n=30 (0.6%) | 5. Sporadic, n=4474 (89.6%) | p value | Adjusted p valuea |
|---|---|---|---|---|---|---|---|---|
| ICA, % (95% CI) | 4738 | 89.5 (85.5, 93.4) | 93.3 (89.1, 97.5) | 92.8 (87.2, 98.3) | 86.2 (73.3, 98.8) | 91.8 (91.0, 92.3) | 0.487 | 0.451 |
| ICA, JDFU, median (range) | 4347 | 64.0 (3.0–2620.0) | 49.0 (3.0–2048.0) | 64.0 (4.0–1024.0) | 47.0 (5.0–1024.0) | 64.0 (3.0–5120.0) | 0.530 | 0.866 |
| IAA, % (95% CI) | 4738 | 49.8 (43.4, 56.2) | 47.4 (39.0, 55.8) | 51.8 (41.1, 62.6) | 55.2 (37.1, 73.3) | 42.2 (40.7, 43.7) | 0.027 | 0.003 |
| 2 vs 3: 0.018 | ||||||||
| 3 vs 5: <0.01 | ||||||||
| IAA, RU, median (range) | 2037 | 9.9 (2.9–260.0) | 13.5 (3.2–338.7) | 9.0 (2.9–48.8) | 10.7 (3.5–484.9) | 10.2 (2.8–7809.0) | 0.437 | 0.447 |
| IA-2A, % (95% CI) | 4738 | 74.3 (68.7, 79.8) | 80.0 (73.3, 86.7) | 74.7 (65.3, 84.1) | 65.5 (48.2, 82.8) | 75.0 (73.7, 76.3) | 0.515 | 0.433 |
| IA-2A, RU, median (range) | 3556 | 102.1 (0.9–223.2) | 99.7 (1.1–202.5) | 110.3 (0.8–185.0) | 121.2 (18.3–186.6) | 105.8 (0.8–553.3) | 0.067 | 0.032 |
| 4 vs 5: 0.058 | ||||||||
| GADA, % (95% CI) | 4738 | 67.1 (61.1, 73.1) | 67.4 (59.5, 75.3) | 69.9 (60.0, 79.7) | 58.6 (40.7, 76.5) | 66.3 (64.8, 67.7) | 0.848 | 0.942 |
| GADA, RU, median (range) | 3144 | 49.8 (5.4–3800.0) | 43.3 (6.3–277.4) | 37.2 (6.4–349.4) | 35.6 (7.4–185.3) | 35.7 (5.4–24,849.0) | 0.826 | 0.192 |
| ZnT8A, % (95% CI) | 4738 | 65.0 (58.9, 71.1) | 63.7 (55.6, 71.8) | 75.9 (66.7, 85.1) | 62.1 (44.4, 79.7) | 69.8 (68.4, 71.1) | 0.141 | 0.243 |
| ZnT8A, RU, median (range) | 3289 | 11.1 (0.5–186.7) | 10.9 (0.6–138.4) | 16.1 (0.6–126.8) | 21.9 (0.6–93.0) | 12.1 (0.5–1201.9) | 0.428 | 0.985 |
| Number of positive antibodies, median (mean) | 4738 | 4 (3.46) | 4 (3.52) | 4 (3.65) | 4 (3.28) | 4 (3.45) | 0.835 | 0.436 |
| Number of positive biochemical antibodies, median (mean) | 4738 | 3 (2.56) | 3 (2.59) | 3 (2.72) | 3 (2.41) | 3 (2.53) | 0.831 | 0.483 |
| Autoantibody negative, % (95% CI) | 4738 | 3.0 (0.8, 5.1) | 3.0 (0.1, 5.8) | 3.6 (0, 7.6) | 10.3 (0, 21.4) | 2.1 (1.7, 2.6) | 0.049 | 0.091 |
| Positivity for multiple (≥2) autoantibodies, % (95% CI) | 4738 | 92.0 (88.5, 95.4) | 94.1 (90.1, 98.1) | 95.2 (90.6, 99.8) | 86.2 (73.7, 98.8) | 92.5 (91.7, 93.2) | 0.542 | 0.552 |
Categorical variables are presented as % (95% CI) and continuous variables as median (range)
In case of significant differences in the analyses between the four familial subgroups and those with sporadic disease, paired comparisons by groups were also performed. Only significant p values are presented from the paired analyses
For comparing frequencies in each study group, cross tabulation and χ2 statistics with continuity correction or Fisher’s exact test when appropriate were used. Differences in levels were determined using Kruskal–Wallis test or the Mann–Whitney U test
Adjustment for confounding factors was performed using logistic/ordinal/multinomial regression for dichotomous/ordinal/categorical variables and quantile regression in R for skewed variables
aAdjusted for sex and age at diagnosis
JDFU, Juvenile Diabetes Foundation unit; RU, relative units