Get 24-hour urine in suspected preeclampsia.(Obstetrics)

BIG ISLAND, HAWAII -- Don't rely on dipsticks to detect proteinuria in pregnant patients with suspected preeclampsia, Dr. Michael A. Belfort said at a conference on obstetrics, gynecology, perinatal medicine, neonatology, and the law.

Instead, get a 24-hour urine collection. If there's not time for that, get a 12-hour urine collection, and order a pregnancy-induced hypertension panel if there is new-onset hypertension, said Dr. Belfort, professor of maternal-fetal medicine at the University of Utah, Salt Lake City.

Dipstick results depend on protein concentrations, which are altered by urine volume. A preeclamptic woman on bed rest will mobilize fluid and increase urine output, potentially diluting urine enough that the protein concentration falls below the minimum level of 20 mg/dL read by dipsticks, he said at the conference sponsored by Boston University.

A dipstick for a woman with 3.2 g of protein in 1,500 cc/day of urine will report 20 mg/dL of protein, erroneously suggesting that only a trace of protein is present. "Until we have more sophisticated ways of determining proteinuria, the dipstick is a screening kit, and the gold standard is 24-hour urine collection," he said.

To diagnose preeclampsia, look for proteinuria (urinary excretion of 0.3 g protein or higher in a 24-hour urine specimen) and new-onset hypertension (at least 140 mm Hg systolic or 90 mm Hg diastolic after 20 weeks' gestation).

Consider not only the blood pressure on a particular day but also the trend in blood pressure over weeks, Dr. Belfort said.

The American College of Obstetricians and Gynecologists recommends checking platelets, liver enzymes, renal function, and 12- or 24-hour urine collection for protein to rule out preeclampsia. If you order lab tests, be sure to get the results, he cautioned.