EDITOR, - Heloise Buys and colleagues have shown that suprapubic aspiration of urine in neonates and young children is a safe procedure and yields good quality specimens.1 Their study confirms the value of bacteriuria as a predictor of urinary tract abnormality in this age group. Analysis of their data also supports our view that pyuria is a poor predictor of urinary tract infection. Thus of 545 specimens examined, 439 were sterile and contained no pus cells and 60 were sterile but contained pus cells; of the 46 that were positive on culture, 24 contained pus cells. The sensitivity of pyuria for detecting bacteriuria is 52% (24/46); the specificity is 88% (439/499). Only 24 of 84 pyuric samples were bacteriuric. The positive predictive value of pyuria for bacteriuria in this study is therefore 29% (24/84), indicating that in this population pyuria is a poor predictor of …