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No differences in HbA1c, FPG in identifying diabetes in adults with tuberculosis
In adults with tuberculosis, both the HbA1c assay and fasting plasma glucose measurement are useful diagnostic tests to screen for type 2 diabetes, although the proportion of false positives was higher for fasting plasma glucose, according to recently published findings.
“Tuberculosis and diabetes, both endemic in many developing countries, are strongly associated with one another; people with diabetes have an increased risk of developing tuberculosis, and may experience delayed recovery and adverse treatment outcomes,” Huma Aftab, a PhD student in the global health section, department of public health at the University of Copenhagen, Denmark, and colleagues wrote. “Methods for diabetes screening in individuals with tuberculosis in low- and middle-income settings should be rapid, low-cost and accurate, should not require fasting, should distinguish between acute and chronic hyperglycemia and should require minimal staff training.”
Aftab and colleagues analyzed data from 268 adults with newly diagnosed, smear-positive tuberculosis who were screened for diabetes at a tertiary hospital in Lahore, Pakistan, using HbA1c, fasting plasma glucose (FPG) and an oral glucose tolerance test (OGTT; 68.7% men; mean age, 35 years; mean BMI, 17.3 kg/m²). Diabetes diagnosis was based on WHO criteria: Thresholds were an HbA1c of at least 6.5% and at least 7 mmol/L for FPG. Researchers used receiver-operating characteristic curves to obtain area under the curve (AUC) with 2-hour plasma glucose as reference; AUCs were compared using a standard algorithm.
Within the cohort, 4.9% (n = 13) were diagnosed with diabetes by OGTT; 11.9% (n = 32) were diagnosed using HbA1c; 14.6% (n = 39) were diagnosed using FPG. Only one participant was diagnosed with diabetes by all three tests. Sensitivity and specificity of an HbA1c threshold of at least 6.5% were 53.8% and 90.2%, respectively. Sensitivity and specificity of the FPG threshold of at least 7 mmol/L were 15.4% and 85.5%, respectively.
The AUC was 0.79 (95% CI, 0.64-0.94) for HbA1c and 0.61 (95% CI, 0.50-0.73) for FPG, with a borderline significant difference between the two tests (P = .07), according to researchers.
“We did not find any significant difference in the performance of HbA1c and FPG in individuals with tuberculosis, but larger studies are needed to recommend one screening method conclusively over others,” the researchers wrote. “Even though HbA1c seems to be the most convenient choice for diabetes screening in individuals with tuberculosis, the high cost and the absence of national standardization programs are major factors hindering the use of this diagnostic method; therefore, we recommend that diabetes screening in individuals with tuberculosis is carried out considering the local context and resources available.” – by Regina Schaffer
Disclosure: This study was supported by a Novo Nordisk Foundation grant. The researchers report no relevant financial disclosures.