Conditions associated with very low values of glycohaemoglobin measured by an HPLC method

AIMS: To identify the causes of very low glycohaemoglobin (GHb) values in a sample of patients with diabetes in southern Brazil using high performance liquid chromatography. METHODS: Between August 1996 and December 2001 all samples from patients with diabetes at a university hospital with GHb values below the reference range (4.7-6.0% HbA(1c)) were submitted to cellulose acetate electrophoresis. Medical records were reviewed to identify conditions that might be associated with these low values. RESULTS: Among 29 657 samples analysed, 130 patients had GHb < 4.7%. Seventy three patients (56%) were heterozygous for HbS, HbC, or HbD (19 black, two mulatto, and 52 white patients). The other 57 patients (44%) without Hb variants had low haematocrit and haemoglobin values (42 patients) or other conditions such as pregnancy, lipaemia, malignancy, cirrhosis, acetylsalicylic acid use, and absence of diabetes (15 patients). CONCLUSIONS: The presence of an Hb variant may falsely lower GHb measurements. However, anaemia is also a source of negative interference. The haematological status should be considered for the correct interpretation of GHb results.