| Characteristics | age group (years) | Chi2 | p-value | ||||
| IHA titer | <20 n (%) | 21 to 30 n (%) | 31 to 40 n (%) | 41 to 50 n (%) | >50 n (%) | ||
| 1:160 or less | 43 (17.62) | 62 (25.40) | 49 (20.1) | 42 (17.21) | 48 (19.67) | 6.7 | 0.9 |
| 1:320 to 1:640 | 37 (16.6) | 46 (20.62) | 49 (21.97) | 44 (19.73) | 47 (21.08) | 5.38 | 0.06 |
| 1:1280 to 1:2560 | 21(20.38) | 21(20.38) | 23 (22.34) | 10 (9.7) | 28 (27.20) | 7.30 | 0.62 |