Which tests are used for pyuria screening in the diagnosis of acute pyelonephritis (kidney infection)?

Updated: Jul 01, 2021
  • Author: Tibor Fulop, MD, PhD, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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The dipstick leukocyte esterase test (LET) helps screen for pyuria. LET results have a sensitivity of 75-96% and a specificity of 94-98% for detecting more than 10 WBC/hpf.

The nitrite production test (NPT) for bacteriuria has 92-100% sensitivity and 35-85% specificity. It may be falsely negative in the presence of diuretic use, low dietary nitrate, or organisms that do not produce nitrate reductase (eg, Enterococcus, Pseudomonas, Staphylococcus). Combined, the LET-NPT has a sensitivity of 79.2% and a specificity of 81%, which is too low for it to be used as the only screening study for bacteriuria.

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