Dipstick measurements of urine specific gravity are unreliable

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 me thods (refractometry, automatic readout of a dipstick (Clinitek-50), and (v isual) 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(R)-50 dip stick U-SG measurements with U-Osm were less than optimal, showing very wid e scatter of values. Only the U-SG refractometer values and U-Osm had a goo d linear correlation. The tested dipstick was unreliable for the bedside de termination of U-SG, even after correction for U-pH, as recommended by the manufacturer. Conclusions-Among the bedside determinations, only refractometry gives reli able U-SG results. Dipstick U-SG measurements should be abandoned.