Table 5.
Number of affected individual children by zygosity (pairs with missing values here excluded), concordance rates and tetrachoric correlations.
| ZYGOSITY | CONCORDANT PAIRS | DISCORDANT PAIRS | PAIRWISE CONCORDANCE | PROBAND WISE CONCORDANCE | TETRACHORIC CORRELATIONS | |
|---|---|---|---|---|---|---|
| AGE 3 | MZM | 12 | 41 | .23 | .37 | .42 |
| MZF | 3 | 41 | .07 | .13 | .18 | |
| DZM | 4 | 54 | .07 | .13 | .25 | |
| DZF | 3 | 32 | .09 | .16 | .25 | |
| DZO | 3 | 76(M) 40(F) | .025 | .05 | .05 | |
| Combined | All MZ | 15 | 82 | .15 | .26 | |
| All DZ | 10 | 202 | .04 | .09 | ||
| AGE 4 | MZM | 19 | 63 | .23 | .38 | .41 |
| MZF | 8 | 54 | .13 | .23 | .36 | |
| DZM | 10 | 71 | .12 | .22 | .27 | |
| DZF | 3 | 54 | .05 | .1 | .16 | |
| DZO | 5 | 111(M) 37(F) | .03 | .06 | .10 | |
| Combined | All MZ | 27 | 117 | .19 | .32 | |
| All DZ | 18 | 273 | .06 | .12 | ||
| AGE 7 | MZM | 6 | 37 | .14 | .20 | .33 |
| MZF | 6 | 20 | .23 | .38 | .49 | |
| DZM | 1 | 40 | .02 | .05 | .08 | |
| DZF | 0 | 17 | .00 | .00 | -0.01 | |
| DZO | 1 | 56(M) 16(F) | .01 | .03 | .07 | |
| Combined | All MZ | 12 | 57 | .17 | .29 | |
| All DZ | 2 | 129 | .02 | .03 | ||
| Recovered group | MZM | 34 | 99 | .25 | .41 | .38 |
| MZF | 34 | 104 | .25 | .40 | .38 | |
| DZM | 20 | 111 | .15 | .26 | .24 | |
| DZF | 13 | 114 | .09 | .19 | .17 | |
| DZO | 23 | 149 (M) 70 (F) | .10 | .17 | .17 | |
| Combined | All MZ | 68 | 203 | .25 | .40 | |
| All DZ | 56 | 444 | .11 | .20 | ||
| Persistent group | MZM | 2 | 15 | .12 | .21 | .40 |
| MZF | 1 | 10 | .09 | .17 | .38 | |
| DZM | 0 | 23 | 0 | 0 | -.14 | |
| DZF | 0 | 11 | 0 | 0 | -.06 | |
| DZO | 0 | 36 (M) 8 (F) | 0 | 0 | -.17 | |
| Combined | All MZ | 3 | 25 | .11 | .19 | |
| 0 | 78 | 0 | 0 | |||
Abbreviations: MZM = monozygotic male, MZF = monozygotic female, DZM = dizygotic male, DZF = dizygotic female, DZO = dizygotic opposite sex
Note. In DZO pairs the two numbers in the discordant column refer to pairs with affected male (M) or female (F) children (i.e. of the 116 discordant DZO pairs at age 3, in 76 of pairs, the male was the stutterer and in the other 40 pairs the femalewas the stutterer). Tetrachoric correlations are estimated in the modeling and indicate the strength of correlation between members of twin pairs for two normally distributed variables that are both expressed as a dichotomy (affected / unaffected).