Further Evaluation of the SG Test Strip for Estimation of Urinary Osmolality

Dörner, Klaus; Campos, Renata Martins; Börnsen, Susanne

doi:10.1515/cclm.1984.22.6.419

Cited by 7 publications

(14 citation statements)

References 3 publications

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“…Furthermore, for the same total ionic concentration, different ions influence the SG reading by variable magnitude. These effects were well demonstrated in an experimental study [13]. In urine specimens with constant osmolality, cations like NH 4 2+ , Ca 2+ and Mg 2+ increased the SG reading disproportionately in comparison to Na + and K + .…”

Section: Influence Of Normal Urinary Constituents On Sg Measurementsupporting

confidence: 59%

“…Among the anions, a similar enhancing effect was seen with phosphates and citrate in comparison to chloride, while acetate, lactate, urate, oxalate and sulfate caused no deviation. In the same study ketone bodies were reported to decrease the reagent strip SG reading [13].…”

Section: Influence Of Normal Urinary Constituents On Sg Measurementmentioning

confidence: 80%

“…The influences of variations in normal urinary composition are apparently much more marked on the reagent strip method. As this method is based on the ionic strength of urine, variations in ionic composition have a significant impact on the SG reading [13]. The basic underlying principle of this method presumes that the ionic and non-ionic constituents in urine are present in constant proportion.…”

Section: Influence Of Normal Urinary Constituents On Sg Measurementmentioning

confidence: 99%

“…However, in practice this is not always true. For instance, the urine from young children has a lower concentration of urea [14] and a higher proportion of ionic constituents [13]. As the SG reading by this method is directly proportional to the ionic concentration of urine [9,15], the SG reading is higher when ionic constituents form the major proportion of osmolality and vice versa.…”

Section: Influence Of Normal Urinary Constituents On Sg Measurementmentioning

confidence: 99%

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Measurement of urinary concentration: a critical appraisal of methodologies

Chadha

Garg

Alon

2001

Pediatric Nephrology

161

143

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The measurement of urine concentration provides information concerning the kidney's ability to appropriately respond to variations in fluid homeostasis. It also assists in the interpretation of other tests performed on the same urine specimen. The gold standard of estimating urinary concentration is the measurement of its osmolality; however, this procedure is not readily available to the practicing physician. Therefore, urine concentration is usually determined by measurement of its specific gravity (SG), which provides a fair estimate of urine osmolality. Over the years numerous tests have been developed to measure urine SG in a simple, quick, reliable and easily available method. These tests measure SG either directly (e.g., gravimetry) or by indirect methods (e.g., refractometry and reagent strip). All these tests have certain limitations based on their underlying physical principles. Specific gravity as measured by refractometry is influenced by proteinuria, such that for each 10 g/l protein the SG increases by 0.003. SG is also influenced by glucosuria such that it increases by approximately 0.002 per 10 g/l glucose when compared with urinary osmolality. Unlike osmolality, which is only affected by the number of particles, refractometry is affected by number, mass and chemical structure of the dissolved particles; hence large molecules like radiographic contrast or mannitol will increase SG relative to osmolality. The reagent strip is minimally affected by glucose, mannitol or radiographic contrast. However, it is affected by urinary pH such that only urine in the pH range of 7.0-7.5 can be correctly interpreted. The measurement of SG by reagent strip is based on the ionic strength of the urine and thus is significantly affected by the ionic composition of the urine and by proteins which have an electric charge in solution. In our experience, SG measured by the refractometer is consistently more accurate than the reagent strip. For the clinician who is interpreting urine SG results, it is important to be aware of these limitations and understand the reasons for possible potential errors of each particular method.

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Section: Influence Of Normal Urinary Constituents On Sg Measurementsupporting

confidence: 59%

Section: Influence Of Normal Urinary Constituents On Sg Measurementmentioning

confidence: 80%

Section: Influence Of Normal Urinary Constituents On Sg Measurementmentioning

confidence: 99%

Section: Influence Of Normal Urinary Constituents On Sg Measurementmentioning

confidence: 99%

See 2 more Smart Citations

Measurement of urinary concentration: a critical appraisal of methodologies

Chadha

Garg

Alon

2001

Pediatric Nephrology

161

143

View full text Add to dashboard Cite

show abstract

“…However, in clinical practice, urine pH is often acidic, especially in the setting of acute kidney injury. USG has not been shown to correlate well with osmolality when urine is acidic in reagent strip testing (6,7), whereas there is no effect of pH on refractometry (5).…”

Section: Introductionmentioning

confidence: 96%