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Urinary C-peptide creatinine ratio practical for measuring insulin in pregnancy
The detectable urinary C-peptide creatinine ratio is a viable method for assessing endogenous insulin secretion in pregnant women with and without diabetes, study data show.
“The ratio of urinary C-peptide to the urinary creatinine obtained from a spot urine sample … is correlated to serum C-peptide outside pregnancy and has been used to assess residual beta-cell function in women with type 1 diabetes,” Ankica Markoska, of the department of investigative medicine at Hammersmith Hospital, Imperial College London, and colleagues wrote. “The current study investigated the use of [urinary C-peptide creatinine ratio] to assess beta-cell function in pregnant women with normal glucose tolerance and with type 1 diabetes.”
The researchers obtained blood and urine samples from 90 glucose-tolerant women who were 28 weeks pregnant during a diagnostic 75-g oral glucose tolerance test. All of the women in the study had at least one risk factor for gestational diabetes or were aged at least 35 years, and all had fasted before the test. Markoska and colleagues also measured two samples each from seven pregnant women with type 1 diabetes. Five women provided samples between the first and third trimester, whereas one provided samples between the first and second trimester, and another provided samples between the second and third trimester.
In the glucose-tolerant women, researchers reported a correlation between the urinary C-peptide creatinine ratio and the serum C-peptide at 0 and 120 minutes during the test (P < .0001). All of the pregnant women had a detectable urinary C-peptide creatinine ratio in the first sample, (median, 49 pmol/mmol; range, 6-1,038 pmol/mmol), Markoska and colleagues reported. This rose in six women by a mean of 477 pmol/mmol (range, 29-1,491 pmol/mmol).
Researchers wrote that the urinary C-peptide creatinine ratio was more practical than a spot serum C-peptide sample because it was easier to collect and process.
“This study demonstrated that [urinary C peptide creatinine ratio] provides a robust and practical means for assessing insulin secretion during pregnancy, and provides a practical methodology to assess in future studies the potential for beta-cell adaptation in women with type 1 diabetes,” Markoska and colleagues wrote. – by Andy Polhamus
Disclosure: The researchers report no relevant financial disclosures.