A-10-year-old boy was recently diagnosed as type I diabetes
mellitus. As a part of work up, an HbA1c (glycosylated
hemoglobin) was sought but could not be done due to presence
of abnormal hemoglobin, later confirmed as HbE trait.
In our experience, we note an increasing
number of children with abnormal hemoglobin and diabetes.
The Diabetes Control and Complications Trial (DCCT) and the
United Kingdom Prospective Diabetes Study (UKPDS)
demonstrated conclusively that risks for complications are
related directly to glycemic control, as measured by HbA1c
[1, 2].
Four basic types of methods are used to
measure HbA1c: immunoassay, ion-exchange high-performance
liquid chromatography (HPLC), boronate affinity HPLC, and
enzymatic assays. All the four methods are ineffective in
assessment of glycemic control in patients homozygous for
HbS, C or SC disease or any other conditions that reduce the
life span of the erythrocytes. In HbAS, AC, AE, AD and F,
the interference of results depend on the method of assay
and the laboratories should be aware of the limitations
of their method with respect to these interferences, as it
turned out in our case [3].
Other parameters of assessing glycemic
control like frequent self monitoring of blood glucose
(SMBG) and glycated albumin (fructosamine) may be used. In
SMBG, cost of the glucometer strips, accuracy and repeated
pricking are limiting factors. For fructosamine, the
non-availability of the assay in many centers and the
standardization of reporting is a problem. Fructosamine
levels usually reflect the average glycemic control in the
previous 2-3 weeks and the frequency of tests has to be
decided based on that. With recent advances, continuous
glucose monitoring system (CGMS) has been introduced where a
catheter is inserted in the subcutaneous plane and is
connected to a computerized glucose sensing apparatus. It
aspirates micro-quantities of interstitial fluid at regular
intervals and records the glucose values which may be
analyzed later. The expected cost of the above system is a
major limiting factor in a resource-constrained setting.
Another test, though not approved by FDA, is 1,5
anhydroglucitol estimation whose concentration normally
falls if blood glucose is above 180mg/dl. Hence, this is
used to assess glycemic variability and reflects more of
post-prandial control [4]. However, in a given situation
like in our patient, these methods have to be resorted to
once in a while to assess the efficacy of the insulin
regimen and diabetes control.
1. Diabetes Control and Complications
Trial Research Group. The effect of intensive treatment of
diabetes on the development and progression of long-term
term complications in insulin-dependent diabetes mellitus. N
Engl J Med. 1993:329:977-86.
2. UK Prospective Diabetes Study (UKPDS)
Group. Intensive blood-glucose control with sulphonylureas
or insulin compared with conventional treatment and risk of
complications in patients with type 2 diabetes (UKPDS 33).
Lancet. 1998;352:837-53.
3. Little RR, Roberts WL. A Review of
variant hemoglobins interfering with hemoglobin A1c
measurement. J Diabetes Sci Technol. 2009;3:446-51.
4. Kim WJ, Park CY. 1,5-Anhydroglucitol in diabetes
mellitus. Endocrine. 2013;43:33-40.
