Multivariable analysis of index episode risk factors for subsequent smear-positive tuberculosis re-treatment (N = 1,733).

PY = Person-years.CI = Confidence Interval.*Adjusted for the other factors shown in the table.†Smear grade at start of treatment:Smear 3+: Any of the two initial smears was 3+, i.e. >10 acid-fast bacilli (AFB) per 1 high-power field (HPF).Smear 2+: Any of the two initial smears was 2+, i.e. 1–10 AFB per 1 HPF, but none of them was 3+.Smear 1+: Any of the two initial smears was 1+, i.e. 10–99 AFB per 100 HPF, but none of them was 2+ or 3+.‡Test for trend.