Falsely negative urinary leucocyte counts due to delayed examination.

Microscopic examination for urinary leucocytes was performed in the ward immediately after micturition and approximately 3 h later at a laboratory. Of the forty-eight specimens classified as positive by counting in the ward, 35% erroneously turned up negative by later counting at the laboratory. Counting of urinary leucocytes should consequently be performed as soon as possible after micturition, probably within 1 h.