Can the urine dipstick test reduce the need for microscopy for assessment of systemic lupus erythematosus disease activity?
OBJECTIVE
Urine microscopic examination is an important component of the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). We investigated whether the urine dipstick test can reduce the need for microscopy for the assessment of SLEDAI.


METHODS
We studied 269 urine samples from 259 SLE patients with Albustix and Hemastix reagent strips. The results were compared to concomitant microscopic examination of urinary sediment.


RESULTS
When trace red blood cell was defined as the cutoff, the sensitivity, specificity, and negative predictive value (NPV) of the Hemastix urine test were 0.98, 0.53, and 0.99, respectively, for hematuria; 0.82, 0.47, and 0.90, respectively, for the presence of pyuria; and 0.91, 0.44, and 0.98, respectively, for the presence of casts by microscopic examination. When proteinuria of 1+ was defined as the cutoff, the sensitivity, specificity, and NPV of the Albustix test were 1.00, 0.46, and 0.99, respectively, for urinary casts; and 0.82, 0.49, and 0.90, respectively, for the presence of pyuria. When both Albustix and Hemastix were applied as screening test, urine microscopy could be reduced by 27%; however, 8% of cases with normal Albustix and Hemastix tests had at least one abnormality on urine microscopy examination.


CONCLUSIONS
In patients with SLE, a combination of Albustix and Hemastix urine tests showed reasonable sensitivity to detect abnormalities in urine sediment. Based on these results, routine urine microscopy can be limited to SLE patients with abnormal Albustix or Hemastix tests. Rarer causes of abnormal renal function in lupus, such as tubulointerstitial nephritis or drug induced interstitial nephritis, would be manifested by pyuria and therefore would not necessarily be detected by changes in the blood and protein detectors on the urine dipstick.
Chan
Rebecca Wing-Yan
RW
Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong, China.
Chow
Kai-Ming
KM
Tam
Lai-Shan
LS
Li
Edmund Kwok-Ming
EK
Wong
Siu Man
SM
Li
Philip Kam-Tao
PK
Szeto
Cheuk-Chun
CC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006417:Hematuria / Q000175:diagnosis / Q000209:etiology / Q000652:urine; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000175:diagnosis* / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011507:Proteinuria / Q000175:diagnosis / Q000209:etiology / Q000652:urine; D011776:Pyuria / Q000175:diagnosis / Q000209:etiology / Q000652:urine; D012372:ROC Curve; D011934:Reagent Strips; D012720:Severity of Illness Index; D016482:Urinalysis
D011934:Reagent Strips