Table 4.
Prevalence of FASD diagnostic concordance and discordance between twin and sibling pairs.
| Concordance and Discordance in FASD Outcomes between Twin and Sibling Pairs | 1. Monozygotic | 2. Dizygotic | 3. Full-siblings | 4. Half-siblings (maternal) | ||||
|---|---|---|---|---|---|---|---|---|
| N = 18 (9 pairs) | N = 78 (39 pairs) | N = 54 (27 pairs) | N = 18 (9 pairs) | |||||
| N pairs | Valid % | N pairs | Valid % | N pairs | Valid % | N pairs | Valid % | |
| Pairwise FASD Diagnoses (FAS, PFAS, SE/AE, ND/AE, Not FASD/AE) | ||||||||
| Concordant outcomes between sibling pairs | ||||||||
| Total concordant pairs | 9 | 100.0 | 22 | 56.4 | 11 | 40.7 | 2 | 22.2 |
| FAS-FAS | 2 | 22.2 | 0 | 0.0 | 0 | 40.7 | 0 | 0.0 |
| PFAS-PFAS | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| SE/AE-SE/AE | 4 | 44.4 | 4 | 10.3 | 2 | 7.4 | 0 | 0..0 |
| ND/AE-ND/AE | 2 | 22.2 | 16 | 41.0 | 6 | 22.2 | 2 | 22.2 |
| Not FASD/AE-Not FASD/AE | 1 | 11.2 | 2 | 5.1 | 3 | 11.1 | 0 | 0.0 |
| Discordant outcomes between sibling pairs | ||||||||
| *Total discordant pairs | 0 | 0.0 | 17 | 43.6 | 16 | 59.3 | 7 | 77.8 |
| FAS-PFAS | 0 | 0.0 | 1 | 2.6 | 0 | 0.0. | 0 | 0.0 |
| FAS-SE/AE | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 1 | 11.1 |
| # FAS-ND/AE | 0 | 0.0 | 0 | 0.0 | 2 | 7.4 | 0 | 0.0 |
| PFAS-SE/AE | 0 | 0.0 | 0 | 0.0 | 1 | 3.7 | 1 | 11.1 |
| # PFAS-ND/AE | 0 | 0.0 | 4 | 10.3 | 2 | 7.4 | 1 | 11.1 |
| SE/AE-ND/AE | 0 | 0.0 | 7 | 17.5 | 5 | 18.5 | 4 | 44.4 |
| SE/AE-Not FASD/AE | 0 | 0.0 | 0 | 0.0 | 2 | 7.4 | 0 | 0.0 |
| ND/AE-Not FASD/AE | 0 | 0.0 | 5 | 12.8 | 2 | 7.4 | 0 | 0.0 |
| Not FASD/AE-Not FASD/AE | 0 | 0.0 | 0 | 0.0 | 2 | 7.4 | 0 | 0.0 |
| Pairwise FASD Diagnostic Features | ||||||||
| Discordant outcomes between sibling pairs | ||||||||
| Growth Ranks 1–4 | ***1 | 11.1 | 17 | 43.6 | 10 | 37.0 | 4 | 44.4 |
| **Face Ranks 1–4: Total discordant pairs | 0 | 0.0 | 10 | 25.6 | 8 | 29.6 | 5 | 55.6 |
| Face Rank 1 vs 4 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| Face Rank 2 vs 4 | 0 | 0.0 | 1 | 2.6 | 1 | 3.7 | 2 | 22.2 |
| Face Rank 3 vs 4 | 0 | 0.0 | 0 | 0.0 | 2 | 7.4 | 0 | 0.0 |
| CNS Ranks 1–4: probability of structural abnormality (none, possible, probable, definite) | ***1 | 11.1 | 17 | 43.6 | 14 | 51.9 | 5 | 55.6 |
| Alcohol Ranks 3–4 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
| CNS Functional Ranks 1–3: (no, moderate, severe dysfunction) | 0 | 0.0 | 17 | 43.6 | 10 | 37.0 | 5 | 55.6 |
| Microcephaly (head circumference <= 3rd percentile) | ***1 | 11.1 | 2 | 5.1 | 5 | 18.5 | 3 | 33.3 |
| Seizure disorder | 0 | 0.0 | 4 | 10.3 | 1 | 3.7 | 1 | 11.1 |
Linear trend across 4 study groups: MH Chi2:
*
10.7, p 0.001;
**
5.1, p 0.02.
***
One twin pair had discordant growth Ranks in their 4-Digit Codes (3244-1244). Another pair had discordant CNS structural Ranks (1243–1233) because only one twin presented with microcephaly. Their CNS functional Ranks, however, were both Rank 3. These contrasts in a single component of the 4-Digit Code did not result in discordant FASD diagnostic classifications. Both twin pairs had concordant diagnoses of SE/AE.
#
Large contrast in pairwise FASD diagnostic outcomes.