Statistical analysis
The sample size was calculated from this formula:
N=Z2pq/d2, Z=1.96, p=0.4, q=0.6,
d=0.07. The study population used, according to the prevalence of thal
in Thailand (30-40%),8,9 was 188, approximating 200
participants (with 10% dropout). Demographic data were summarized as
frequency and percentage for qualitative data and as mean and SD for
quantitative data. Student’s t or Mann-Whitney U test was used to
compare continuous variables; the chi-square or Fisher’s exact test was
used for categorical variables, as appropriate. Univariate and
multivariate logistic regression analysis was performed to identify risk
factors. A P of <0.05 was considered statistically
significant.