Uncertain clinical utility of contemporary strategies for microalbuminuria testing.
OBJECTIVE
To determine whether conventional dipstick tests for proteinuria accurately identified patients with diabetic nephropathy and whether repeat testing for elevated albumin excretion and screening for urinary tract infection was required as part of the screening process for microalbuminuria.


METHODS
Random urine for albumin/creatinine ratio (ACR) was measured in all patients over a 6-month period. Patients who had a positive test (>3.5 mg/mmol) were requested to provide two further samples for re-testing and a mid-stream urine specimen to screen for asymptomatic bacteriuria. The evaluation of accuracy of dipstick proteinuria was carried out in the samples collected over a fixed 2-week period.


RESULTS
Dipstick vs. ACR--Of 221 samples collected, 142 were negative, 58 had 1+ and 21 had 2+ or more for dipstick proteinuria. At a threshold of 2+, the majority (81%) had ACR in the overt nephropathy range (>30 mg/mmol) and none had it below 10 mg/mmol, whereas at 1+, only 28% had ACR in the overt nephropathy range and 19% even had normoalbuminuria. Repeat Testing--Of the 1832 patients who had microalbuminuria measured, 673 had a positive test and 248 returned repeat samples. Eighty-one patients returned two samples, of which 16 had discordant results, and 161 patients gave three samples, of which only 23 were false positives. The majority of these 39 patients had low-grade microalbuminuria (ACR 3.5-10 mg/mmol) in their first sample. The absolute benefit of repeat testing was only to 3.4% of the population who screened positive, while in a further 2.3% (two-sample responders) there was potential for confusion because of discordant results. Infection Screening--Of the 248 samples, only 31 had evidence of urinary infection.


CONCLUSIONS
Dipstick proteinuria of 1+ does not necessarily represent significant nephropathy. There is little or no benefit in repeat testing outside of the low microalbuminuria range but compliance to such testing is poor. Screening for asymptomatic bacteriuria as part of microalbuminuria screening is of questionable value.
Baskar
V
V
Wolverhampton Diabetes Centre, New Cross Hospital, Wolverhampton, UK. baskar@doctors.org.uk
Kamalakannan
D
D
Holland
M R
MR
Catchpole
C R
CR
Singh
B M
BM
D000419:Albuminuria / Q000175:diagnosis*; D006801:Humans; D011507:Proteinuria / Q000175:diagnosis; D011934:Reagent Strips; D012008:Recurrence; D019233:Retreatment; D014552:Urinary Tract Infections / Q000175:diagnosis
D011934:Reagent Strips