Spot Urine Samples for Assessing Proteinuria in Suspected Pre-Eclampsia

Estimates of the protein-to-creatinine ratio in spot urine samples may be of value in evaluating proteinuria in pregnant women with suspected pre-eclampsia, according to a meta-analysis in the British Medical Journal.

The meta-analysis included data from 13 studies evaluating the urinary spot protein-to-creatinine ratio or albumin-to-creatinine ratio for the detection of significant proteinuria in pregnant women with hypertension. All studies provided data on 24-hour urinary protein excretion results or adverse pregnancy outcomes.

Studies evaluating the protein-to-creatinine ratio showed significant variation in threshold values and in estimated sensitivities and specificities. The optimum threshold values ranged between 0.30 and 0.35, on average. However, none of the threshold values had estimated sensitivity and specificity greater than 80 percent. Estimates of accuracy showed significant heterogeneity.

For studies using the albumin-to-creatinine ratio, no meta-analysis could be performed. One study reported that a value greater than 2 mg/mmol (according to the DCA 2000 quantitative analyzer) had the highest predictive value for significant proteinuria—sensitivity and specificity were both 94 percent. A study including information on pregnancy outcomes reported 82 percent sensitivity for perinatal death, with specificity of 59 percent. A meta-analysis of results from studies of albumin-to-creatinine ratio was 0.82, with specificity of 0.59.

A quick and accurate method is needed to identify significant proteinuria in women with suspected pre-eclampsia. On the basis of available evidence, the estimated protein-to-creatinine ratio in spot urine samples is a promising test for this purpose. More research will be needed to clarify the clinical value of this test, to assess the use of the albumin-to-creatinine ratio, and to evaluate the ability to predict adverse pregnancy outcomes with either test [Morris RK, et al. Diagnostic accuracy of spot urinary protein and albumin to creatinine ratios for detection of significant proteinuria or adverse pregnancy outcome in patients with suspected pre-eclampsia: systematic review and meta-analysis. BMJ 2012; 345:e4342].

September 2012 (Vol. 4, Number 9)