Côté AM et al. (2008) Diagnostic accuracy of urinary spot protein:creatinine ratio for proteinuria in hypertensive pregnant women: systematic review. BMJ 336: 1003–1006

A 24 h urine collection is the standard test by which proteinuria is assessed. This test can produce misleading results, however, especially during pregnancy, in part because of the difficulty associated with sample collection. The spot protein:creatinine ratio is an alternative test that is often used to assess proteinuria, but its efficacy in detecting proteinuria in pregnant women is unknown. This test could be especially useful in the evaluation of pre-eclampsia, as the condition is characterized by hypertension and proteinuria.

Côté et al. conducted a literature review of 13 studies in which the spot protein:creatinine ratio was used to asses proteinuria (≥0.3 g/day) in pregnant women with hypertension. In all, eight different cut-off points for determination of proteinuria were used (median 24 mg/mmol, range 17–57 mg/mmol). Of these studies, nine had sufficient data to calculate diagnostic accuracy with a cut-off point of 30 mg/mmol, as is recommended by published guidelines. In this subgroup of studies, the sensitivity and specificity of the test were 83.6% (95% CI 77.5–89.7%) and 76.3% (95% CI 72.6–80.0%), respectively. The negative likelihood ratio was fair to good (median 0.21, 95% CI 0.13–0.31), suggesting that a spot protein:creatinine ratio of <30 mg/mmol is an appropriate threshold for ruling out proteinuria.

The authors conclude that the spot protein:creatinine ratio is a time-efficient and convenient tool to aid in the diagnosis of pre-eclampsia in pregnant women with hypertension.