Accuracy of Fasting Capillary Blood Glucose by Glucometer for Screening of Gestational Diabetes Mellitus: Simplicity is the Key

  • NAYAB AFZAL Consultant Chemical Pathologist, Laboratory Services, National Medical Center, National Highway, Defence Phase 1, Karachi.


Objective: The objective of this study is to assess the diagnostic accuracy of fasting capillary blood glucose (CBG) using glucometer for screening of Gestational Diabetes Mellitus (GDM).

 Methodology: Pregnant women in their second or third trimester, who visited the laboratory for 75 gm Oral Glucose Tolerance Test, were included in the study. Fasting CBG was measured using a glucometer and simultaneous fasting venous plasma glucose (VPG) levels were analyzed on fully automated chemistry analyzer. Using the American Diabetic Association (ADA) criteria, patients with fasting VPG levels>92 mg/dl were labeled as having GDM. Diagnostic accuracy of CBG was presented in terms of sensitivity, specificity, predictive values and likelihood ratios.

Results: Total number of patients were 713, out of which 33 (4.62 %) were diagnosed as having GDM, according to ADA criteria. Mean maternal age was 29.00+4.63 years, mean gestational age was 26.54+5.28 weeks, mean weight was 67.28+10.24 kg and mean BMI was 26.07+3.96 kg/m2. Mean fasting CBG was 89.94+7.17md/dl, mean fasting VPG was 84.06+7.32 mg/dl, mean difference between two values was 5.89+3.17mg/dl. Pearson’s correlation was 0.904(p-value<0.001).  Fasting CBG by glucometer had sensitivity 96.97%, specificity 78.24%, positive predictive value 17.78%, negative predictive value 99.81%, positive likelihood ratio 4.46 and negative likelihood ratio 0.04. Diagnostic accuracy of fasting CBG by glucometer was 79.10%.

Conclusion: Fasting CBG is a simple, cost effective, rapid and convenient method. It can be recommended for screening of GDM in pregnant women especially at health care centers where automated analyzers are not available.

Keywords: GDM, Screening, Diagnosis, fasting capillary blood glucose.

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