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Dipstick measurements of urine specific gravity are unreliable
  1. A S de Buys Roessingh,
  2. A Drukker,
  3. J-P Guignard
  1. Renal Unit, Department of Paediatrics, University Medical Centre (CHUV), CH-1011 Lausanne, Switzerland
  1. Prof. GuignardJean-Pierre.Guignard{at}chuv.hospvd.ch

Abstract

AIM To evaluate the reliability of dipstick measurements of urine specific gravity (U-SG).

METHODS Fresh urine specimens were tested for urine pH and osmolality (U-pH, U-Osm) by a pH meter and an osmometer, and for U-SG by three different methods (refractometry, automatic readout of a dipstick (Clinitek-50), and (visual) change of colour of the dipstick).

RESULTS The correlations between the visual U-SG dipstick measurements and U-SG determined by a refractometer and the comparison of Clinitek®-50 dipstick U-SG measurements with U-Osm were less than optimal, showing very wide scatter of values. Only the U-SG refractometer values and U-Osm had a good linear correlation. The tested dipstick was unreliable for the bedside determination of U-SG, even after correction for U-pH, as recommended by the manufacturer.

CONCLUSIONS Among the bedside determinations, only refractometry gives reliable U-SG results. Dipstick U-SG measurements should be abandoned.

  • urine specific gravity
  • dipstick urinalysis
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