Statistical analysis
Quantitative variables as mean ±
SD and qualitative variables also were reported as frequency (%).
Chi-square and Fisher’s exact tests were used for categorical variable
comparison. In addition, to compare the median of quantitative variables
in the two groups test was used. Then, first to determine the factors
associated with the positiveness of HRCT result univariate logistic
model was fitted, and those variables which had P < 0.25 were
entered into the multiple model. Receiver operating characteristic (ROC)
curves were constructed to test the ability of final model to predict
the positiveness of HRCT result. All analysis was carried out in the
version 20.0 and STATA Release version 12. P<0.05 was
considered statistically significant.