Glycosylated Haemoglobin (HbA1c) as a Diagnostic Criterion for Hyperglycaemia First Detected in Pregnancy

The study was prompted by the high prevalence of hyperglycaemia first detected in pregnancy (HIP) which is classified into diabetes mellitus in pregnancy (DIP) and gestational diabetes mellitus (GDM). This study aimed to determine the usefulness of Glycosylated Haemoglobin (HBA1c) in the diagnosis of HIP in the first trimester of pregnancy.

The study was of a prospective cross-sectional design carried out between January 2020 and August 2020 at the University of Port Harcourt Teaching (UPTH) and Rivers State University Teaching Hospital (RSUTH). Three hundred and five consecutive pregnant women attending the antenatal clinic at 8 to 13 ⁺⁶ weeks of pregnancy were recruited for the study. Patients' socio-demographic information, anthropometric measurements, and medical, obstetric, and gynaecological history were recorded on a predesigned proforma. Blood was taken for an oral glucose tolerance test (OGTT) and glycosylated haemoglobin (HBA1c) levels. Ethical approval for the study was obtained from the Research Ethics Committee of the UPTH and RSUTH.

The prevalence of DIP, GDM, and HIP in the study was 2.62%, 28.85%, and 31.48% respectively. The ROC curve for HbA1c in the study showed a significant area under the Curve (AUC) value of 0.653%, 95% CI = 0.59 - 0.72, p = 0.001. The Youden index reached 2.50 and the optimal cut-off for HBA1c for diagnosis of diabetes was 5.25%. The sensitivity, specificity, PPV, and NPV for HbA1c against the Gold standard OGTT in the diagnosis of GDM were 36.5%, 88.5%, 59.3, %, and 75.2% respectively. HbA1c had high specificity and moderately high NPV.

Glycosylated haemoglobin was a fairly good tool for diagnosis of HIP in the first trimester, but it could not replace OGTT which is the gold standard.