Between January 2008 and June 2011, we identified newly diagnosed childhood
AL cases (less than 15 years old) in Shanghai. A 1:1 matched caseecontrol study
design was used. The selection criteria are published elsewhere (Ding et al., 2012).
Briefly, newly diagnosed (less than 2 wk) childhood AL according to the FrenchAmerican-British classification and admitted to four children’s hospitals in
Shanghai were recruited in the study. The control subjects were healthy children
who received physical check-up from the department of children’s healthcare or
who visited the clinic of developmental pediatrics or orthopedics for reasons other
than blood diseases and malignant tumors. To ensure that cases and controls were
comparable in terms of socioeconomic category, the controls were selected from the
same hospital as cases and were matched with cases in gender and age (1 y). Both
cases and controls had resided in the same home before diagnosis/reference date for
at least one year. Children who had been adopted were not eligible as either cases or
controls