Table 2.
Results of meta-regression analysis Duchenne Muscular Dystrophy (DMD) prevalence and birth prevalence
| Outcome | Subgroup | Study-level covariate(s) included into the meta-regression | Heterogeneity assessment | |||||
|---|---|---|---|---|---|---|---|---|
| Covariate(s) selected | p-value* | Cochran’s Q (df) | p-value (Q test) | I2 (%) | Between-study variancee | R2 (%)f | ||
| DMD prevalence | Males only (15 studies) | None (random-effects MA) | – | 856.4531 (df = 14) | < 0.0001 | 98.46% | 0.4741 | – |
| Continenta | 0.2027 | 450.7452 (df = 12) | < 0.0001 | 97.90% | 0.3857 | 18.65% | ||
| Study year (begin) + Study duration | 0.4195 | 632.8951 (df = 12) | < 0.0001 | 97.89% | 0.4227 | 10.84% | ||
| Study designc | 0.6429 | 572.9228 (df = 12) | < 0.0001 | 98.40% | 0.4452 | 6.10% | ||
| DMD birth prevalence | All (27 studies) | None (random-effects MA) | – | 82.0309 (df = 26) | < 0.0001 | 89.79% | 0.1646 | – |
| Continentb | 0.9308 | 74.7046 (df = 23) | < 0.0001 | 88.90% | 0.1619 | 1.64% | ||
| Study year (begin) + Study duration | 0.0012 | 60.8329 (df = 23) | < 0.0001 | 83.13% | 0.0905 | 45.02% | ||
| Study designd | 0.3189 | 78.8714 (df = 24) | < 0.0001 | 87.51% | 0.1483 | 9.90% | ||
MA Meta-analysis, I2 Measure of inconsistency, df Degrees of freedom referred to the Cochran’s Q test
*P-values from omnibus Wald-type test of parameters (i.e. study-level covariates included into the model)
aContinents were regrouped as follows: America North (US and Canada) (4 studies), Europe North/Centre/East (8 studies), Others (Asia East and Africa South) (3 studies)
bContinents were regrouped as follows: America North (US and Canada) (4 studies), Asia East and Australia/New-Zealand (4 studies), Europe Centre/East/South (13 studies), Europe North (6 studies)
cStudy designs were regrouped as follows: Observational cohort (3 studies), Retrospective cohort/chart-review/cross-sectional (9 studies), epidemiological survey (3 studies)
dStudy designs were regrouped as follows: Cross-sectional (10 studies), Prospective cohort and survey (8 studies), Retrospective cohort/chart-review (9 studies)
eTotal and residual between-study variance: the overall heterogeneity corresponds to the total between-study variance estimated from random-effects MA whereas the residual heterogeneity corresponds to between study-variance explained by the study-level covariates included into meta-regression model
fR2 is the proportion of the overall heterogeneity (i.e. the total between-study variance) which is “explained” (i.e. reduced) by the effect of the included study-level covariate