Glycemic assessment in diabetic patients with secondary polycytheamia: limitations of HbA1c and the potential role of fructosamine—a prospective comparative study

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Erarslan S., Paşalı Kilit T., Acet A.

ACTA DIABETOLOGICA, vol.1, no.1, pp.1-6, 2026 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 1 Issue: 1
  • Publication Date: 2026
  • Doi Number: 10.1007/s00592-026-02735-z
  • Journal Name: ACTA DIABETOLOGICA
  • Journal Indexes: Academic Search Ultimate (EBSCO), Natural Science Collection (ProQuest), Biological Science Database (ProQuest), Biomedical Reference Collection: Corporate Edition (EBSCO), Health Research Premium Collection (ProQuest), Scopus, Pharma Collection (ProQuest), Science Citation Index Expanded (SCI-EXPANDED), BIOSIS, EMBASE, MEDLINE
  • Page Numbers: pp.1-6
  • Open Archive Collection: AVESIS Open Access Collection
  • Kütahya Health Sciences University Affiliated: Yes

Abstract

Objective This study aimed to evaluate the reliability of haemoglobin A1c (HbA1c) for assessing glycaemic status in

patients with type 2 diabetes mellitus (T2DM) and secondary polycythaemia, and to determine whether fructosamine serves

as a more reliable complementary glycaemic marker in this population.

Methods In this prospective observational study, patients with T2DM and secondary polycythaemia (n = 62) and T2DM

controls with normal haematological indices (n = 40) were enrolled. HbA1c- and fructosamine-derived estimated mean

plasma glucose (eMPG) were compared with structured home capillary blood glucose (CBG; 7 measurements/day × 5 days).

Bland-Altman analysis and multivariate linear regression (adjusting for age, sex, diabetes duration, BMI, smoking, fasting

glucose, haemoglobin, haematocrit) were performed.

Results Fasting plasma glucose and HbA1c were similar between groups (p = 0.352 and p = 0.816), while fructosamine

(456.53 ± 90.18 vs. 404.18 ± 97.63 μmol/L; p = 0.001) and Home-CBG (207.23 ± 49.18 vs. 181.98 ± 55.31 mg/dL; p = 0.002)

were significantly higher in the polycythaemia group. Bland-Altman analysis confirmed a systematic negative bias of

HbA1c-derived eMPG (mean bias: −23.73 mg/dL; 95% LoA: −45.97 to − 1.48). On multivariate regression, polycythaemia

group assignment was the strongest independent association with HbA1c underestimation (β=−16.80 mg/dL; 95% CI:

−25.53 to − 8.07; p < 0.001). Fructosamine-derived eMPG showed substantially better agreement with Home-CBG (bias:

+7.68 mg/dL). Overall, 60% of polycythaemia patients would have been assigned to a different glycaemic control category

based on fructosamine versus HbA1c.

Conclusion HbA1c systematically underestimates glycaemic status in patients with polycythaemia and may lead to clinically

relevant misclassification. In contrast, fructosamine appears to provide a more reliable estimate of glycaemic control

in this population.