Early prediction of pre-eclampsia by measurement of kallikrein and creatinine on a random urine sample

Objective To assess the measurement of inactive urinary kallikrein (IUK) to creatinine (Cr) ratio (IUK:Cr) on an untimed urine sample, collected between 16 and 20 weeks of pregnancy, as a predictive test for the development of both proteinuric and nonproteinuric pre-eclampsia. Design A prospective longitudinal study. Setting A clinic for anternatal care and a university research department. Participants Three hundred and seven normotensive women randomly selected (124 nulliparous and 183 parous) attending the antenatal clinic for their booking visit. Main outcome measures 1. Nonproteinuric pre-eclampsia: a rise in diastolic blood pressure of 25 mmHg or more and a crossing of the threshold of 90 mmHg; 2. Proteinuric pre-eclampsia: same as 1. plus the development of significant proteinuria (> 1(+) on urine dipstick). Results Thirty-seven women developed pre-eclampsia, 12 of whom had proteinuria. Median IUK:Cr ratio in this group was 78.27, compared with 358.19 in the remainder. Analysis of receiver-operator characteristics gave an area under the curve of 0.803. An IUK:Cr ratio of 170 or less in this study predicted nonproteinuric or proteinuric pre-eclampsia with a sensitivity of 70% and a specificity of 86%. Ten of the twelve women who had proteinuria had an IUK:Cr below 170. Median IUK:Cr for those with proteinuric pre-eclampsia was 72.91. Conclusions Measurement of IUK:Cr on a urine sample, collected between 16 and 20 weeks of gestation, represents a simple and practical test for the risk of subsequent pre-eclampsia, with a sensitivity and specificity comparable to those reported by other investigators using the widely recognised, but less practical, angiotensin II sensitivity test.