Clinical value of a urinary test strip for identifying individuals with poor vitamin C status

In a recent study, we screened 135 healthy, nonsmoking subjects (24.410.7 years of age, mean ±SE; 62 males, 73 females) from a campus population. Two percent of the sample had plasma vitamin C (VC) levels indicative of scurvy (≤11 u,mol/L, n=3), and 18% of the sample had subnormal plasma VC levels (≤28 μmol/L, n=24). The average intake of fruits and vegetables in the sample was 2.3+1.8 servings per day. The present study examined the incidence of scorbutic and subnormal VC status in an outpatient population (n=494) and the clinical value of a urinary VC test strip, C-Strips® (Wholesale Nutrition Club, Saratoga, CA). Nearly 9% of the outpatient population (n=43) had plasma VC levels indicative of scurvy, and 35% of the population (n=175) had subnormal plasma VC levels. The urinary test strip contained the dye 2,6-dichlorophenolindophenol and turned colorless in the presence of VC. The amount of VC in urine was inversely related to the seconds it took the strip to turn % white (r=-47, p<001). Plasma VC was correlated to urinary VC (r=0.52, p<.001). The 'seconds to turn strip % white' was significantly reduced only when plasma VC levels rose above 45 μmol/L (0.8 mg%), a level indicative of ample VC nutriture. Test strips which did not turn % white within 2 minutes would identify individuals with subnormal VC status (plasma VC <28 junol/L) with 70% reliability; thus a false negative would occur in 30% of cases. In conclusion, poor vitamin C status was common in our outpatient population; however, the urinary test strips were useful only in identifying individuals with ample vitamin C status.