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Proteinuria is a major feature of renal involvement in systemic lupus erythematosus (SLE), and therapeutic adjustments are often made on the basis of this proteinuria ( 1-5). Quantitation of proteinuria has usually required the use of a 24-hour urine collection (6). Poor patient compliance and delay in obtaining results have made this method of collection much less than optimal, particularly in an outpatient setting in a major referral center. We here report the results of quantitating proteinuria by hsing a ratio of protein to creatinine concentration in a random, spot urine collection. Other investigators have attempted to use similar, though not necessarily identical, ratios for estimation of 24-hour urine uric acid (7) and metanephrine excretion (8). METHODSTwenty-five urine samples were collected from 18 patients with SLE who met American Rheumatism Association criteria (9). Sixteen patients were selected because of dipstick proteinuria on routine urinalysis. Two patients with SLE without dipstick proteinuria were purposely selected, each representing a single collection (Figure 1). Each sample was refrigerated, and each collection included a randomi spot urine (225 ml) and a 24-hour urine specimen, both obtained within a 48-hodr period. Collections during menstruation, urinary tract infections, and post renal biopsy were excluded because of potential extraneous protein contamination. Five patients had more than 1 sample collection, at least 1 month apart, with no attempt to hold therapy constant. No attempt has been made by the authors to assess the accuracy of this method in other types of proteinuria.Appropriate aliquots of each urine sample were filtered through Whatman # 1 paper. Protein concentration was determined, in duplicate, by the modified standard biuret method (10) (normal concentrations <150 md24 hours). Creatinine was determined by the kinetics method, using a commercially available kit (Gilchem, Gilford Diagnostics, Cleveland, OH) (normal range 0.9-1.5 gm/24 hours).Data analysis was performed by linear regression. RESULTSThe protein concentration alone in the spot urine specimen did not consistently equal the protein concentration in the 24-hour specimen. This result was expected. In our patients, 24-hour urine protein ranged from 0 to 10 grams, and serum creatinine values ranged from 0.7 to 2.5 mgldl. There was a strong linear

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