P osm, U sg, and U osm appear sensitive to incremental changes in acute hypertonic dehydration, however, the misclassified outcomes for U sg and U osm raise concerns.
At the most accurate cut-off values, 1.015 and 1.020 for U sg and 700 m osm/kg and 800 m osm/kg for U osm, only 65% of the athletes were correctly classified using U sg and 63% using U osm. Using the medical decision model, sensitivity and specificity were not significant at selected cut-offs for U sg and U osm. Incremental changes in P osm were observed as subjects dehydrated by 5% of body weight and rehydrated while U sg and U osm showed delayed dehydration-related changes. This investigation: 1) compared sensitivity of urine specific gravity (U sg), urine osmolality (U osm) and a criterion measurement of hydration, plasma osmolality (P osm), at progressive stages of acute hypertonic dehydration and 2) using a medical decision model, determined whether U sg or U osm accurately reflected hydra-tion status compared to P osm among 51 subjects tested throughout the day. Therefore, the correct SG was reported as 1.087 (i.e., 1 + 0.029 × 3).To reduce the adverse consequences of exertion-related and acute intentional dehydration research has focused on monitoring hydration status. The sample was diluted with 2 volumes of water, giving a reading of 1.029 by refractometer. The use of a radiographic contrast agent during the computed tomography examination was the cause of the discrepant SG results. Although urinalysis demonstrated significant. Osmolality is affected by glucose but not by contrast agents ( 1, 2). A 46-year-old woman with poorly controlled type 2 diabetes complained of polyuria with a daily output of 5 L. In contrast, reagent strips measure ionic strength and are not affected by protein, glucose, or contrast agents. High molecular weight substances such as glucose, protein, or radiographic contrast agents will have a greater effect on the SG ( 1, 2).
Urine osmolality and specific gravity lab values manual#
Refractometry (the principle of the Urisys 2400 SG and the manual refractometer) measures the refractive index, which is related to the total mass of solutes present in the urine. With dehydration, the urine osmolality should be 3 to 4 times the plasma osmolality. SG is defined as the density of a liquid compared with that of distilled water at the same temperature ( 1). The normal kidney can concentrate a urine to 800 to 1,400 mosmol/kg and with excess fluid intake, a minimal osmolality of 40 to 80 mosmol/kg can be obtained. What other approaches could be taken to report an SG for this sample? The urine specific gravity (SG) is determined using a refractometer designed for veterinary samples, which includes a scale calibrated specifically for cat. Which method is suitable for SG measurement of this sample?
Why was urine SG unreportable by Urisys 2400 and refractometer? The urine osmolality was 500 mOsm/kg (adult reference interval, 50–1200 mOsm/kg). The urine osmolar gap is described as the sum of urinary concentrations of sodium, potassium, bicarbonate, chloride, glucose, and urea compared to measured. A manual repeat of the SG measurement was also not readable by refractometer (no boundary line on the scale) but was 1.015 according to Roche Chemstrips®. A routine urinalysis with the Roche Urisys® 2400 indicated the specific gravity (SG) as a flag, i.e., an error for SG. Three hours later, his clear yellow urine sample was sent to the laboratory. A 21-year-old man presented after being struck by a car and underwent a computed tomography scan of the chest and spine.
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