INADEQUACY OF DIPSTICK PROTEINURIA IN HYPERTENSIVE PREGNANCY

The objective of this study was to determine the accuracy of ward urin alysis and the sensitivity of dipstick testing in the assessment of pr oteinuria in hypertensive pregnant women. Subjects were 230 consecutiv e hypertensive pregnant women who were admitted to hospital over a 2-y ear period. Routine ward urinalyses for protein, obtained on a mid-str eam sample before and after a 24-hour urine collection for quantitatin g proteinuria, were compared with the 24-hour urine protein excretion. As a control for dipstick accuracy, urinalysis was also performed on a mixed aliquot of each of the 24-hour samples by a single observer ex perienced in urinalysis. True proteinuria was considered as >300 mg/da y. The positive predictive value for urinalysis ranged from 38% (for t he precollection test) to 60% (for tests on the aliquot). Negative pre dictive values were 86-88%. The false negative rates at 'nil' or 'trac e' proteinuria ranged from 8-18%. The false positive rates at '3+' (3 g/L) or '4+' (greater than or equal to 20 g/L) ranged from 0-17%, at ' 2+' (1 g/L) from 18-50% and at '1+' (0.3 g/L) from 67-83%. Best result s for urinalysis were obtained on the aliquot testing but even under t hese ideal circumstances there was a high false positive rate (67%) at '1+' (0.3 g/L) urinalysis level. These studies show that in routine c linical practice 'nil' or 'trace' proteinuria will miss significant pr oteinuria in approximately 1 out of 8 hypertensive pregnant women whil e '3+'(3 g/L) or '4+'(greater than or equal to 20 g/L) will rarely be a false positive. At urinalysis of '1+' or '2+' a 24-hour urine collec tion is required to be certain about the presence or absence of protei nuria. Research studies should demand 24-hour urine protein quantitati on and not rely solely upon urinalysis results.