Short communication The effect of aspirin and vitamins C and E on HbA 1c assays Joíza L. Camargo a, ⁎ , Jonathas Stifft b , Jorge L. Gross b a Clinical Pathology Department, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil b Endocrinology Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, RS, Brazil Received 13 March 2006; received in revised form 24 March 2006; accepted 25 March 2006 Available online 15 May 2006 Abstract Background: Aspirin (ASA) and vitamins C and E may inhibit non-enzymatic glycation in vivo and may also interfere with HbA 1c assays, masking true results. We investigated the effect of usual doses of ASA, vitamin C and E on HbA1c levels in a group of non-diabetic volunteers. Methods: A randomized clinical trial was performed with 28 healthy non-diabetic individuals. Subjects were allocated to take ASA 200 mg/day, vitamin C 1 g/day, vitamin E 400 mg/day, or to a control group, for a period of 4 months. Blood samples were collected at baseline and at monthly intervals for HbA1c analysis by HPLC Variant II (BioRad), HPLC L-9100 (Merck – Hitachi) and Tina Quant® HbA 1c II immunoassay (Roche). Results: HbA 1c levels of the control, vitamin C and E groups did not change throughout the study, independently of the method used. HbA 1c measured by Hitachi L-9100 HPLC increased significantly (P = 0.033) at 4 months after ASA intake, although this increase was of only 0.17%. Conclusions: Treatment with vitamins C and E in pharmacological doses does not have any impact on HbA1c measurements in non-diabetic patients with the three methods employed. ASA induces a modest, not clinically relevant, increase in HbA1c levels with one of the methods. © 2006 Elsevier B.V. All rights reserved. Keywords: Glycemic control; Glycohemoglobin; Ascorbic acid; Acetyl salicylic acid; Tocopherol 1. Introduction After 2 landmark studies – the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospec- tive Diabetes Study (UKPDS) – glycated haemoglobin (HbA1c) became the reference parameter to evaluate metabolic control in patients with diabetes [1,2]. Ideally, the assay employed to measure HbA1c should be traceable to the DCCT/UKPDS values [3]. Furthermore, the correct interpretation of HbA1c results by physicians requires knowledge of factors that may possibly interfere with HbA1c test results, such as intake of aspirin (acetyl salicylic acid, ASA) and vitamins C and E [4]. ASA is indicated for all patients with diabetes above N 30 years and without any contra-indications to decrease the risk of myocardial infarction [5]. ASA promotes acetylation of HbA1c chains, altering the net protein charge. This acetylated product may comigrate with the A 1c fraction in assays that are based on charge separation, such as ion exchange chromatog- raphy, and it also inhibits in vivo non-enzymatic protein glycation through a site competition mechanism [4]. Both these effects could affect HbA 1c results in opposite directions. Although the use of vitamins C and E might have a protective role in the development of diabetic microvascular complications [6], recent clinical trial did not observe any effect of these vitamins on cardiovascular outcomes and nephropathy in patients with and without diabetes [7]. Vitamins C and E have been reported to decrease protein glycation [8,9], although some reports do not confirm these findings [10,11]. In addition, cross- sectional studies have shown a negative association between the intake of vitamin C and/or E and levels of HbA1c [12]. Therefore the aim of this study was to investigate the effect ASA and of vitamins C and E on HbA1c levels in a group of non-diabetic volunteers. 2. Materials and methods 2.1. Study design This study followed a randomized control trial design. Subjects were randomized and allocated to take ASA (Aspirin, Clinica Chimica Acta 372 (2006) 206 – 209 www.elsevier.com/locate/clinchim ⁎ Corresponding author. Serviço de Patologia Clínica, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcellos 2350, 2 0 andar, 90035-903, Porto Alegre, RS, Brazil. Fax: +55 51 21018310. E-mail addresses: jcamargo@hcpa.ufrgs.br (J.L. Camargo), jorgegross@terra.com.br (J.L. Gross). 0009-8981/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.cca.2006.03.031