Accuracy and influence of ascorbic acid on glucose-test with urine dip sticks in prenatal care.

OBJECTIVE

In Germany, urine analysis with dip sticks are used for screening of gestational diabetes. Our goal was to find the cut-off levels of glucose dip sticks and evaluate the influence of ascorbic acid on the result.

STUDY DESIGN

We took urine samples of 152 pregnant patients between 01/2004 and 10/2004. The glucose content of the urine was analyzed using several dip sticks (Combur10 Roche, Multistix 8SG Bayer, Diabur5000 Roche and by the hexokinase method. The ascorbic acid concentration of the specimen was determined.

RESULTS

Glycosuria test dip sticks have a good sensitivity and specificity of the expected positive/negative-reaction compared with the hexokinase method but showed a significant reduction of the color reaction at high concentrations of ascorbic acid.

CONCLUSION

High ascorbic acid concentrations cause a reduction in the color reaction of urine dip sticks. False-negative test stick measurements can appear in patients with low glycosuria. The rate of glycosuria shows high individual differences and dependent on the concentration of vitamin C. We conclude that dip sticks are not useful in prenatal management.