A patient who claims optimum management for diabetes mellitus may show persistently high hemoglobin A1c levels. These apparently contradictory findings should be investigated to determine the cause.


Possible explanations:

(1) falsification of apparent glucose control by the patient, as a form of malingering

(2) hemoglobinopathy giving a falsely high hemoglobin A1c result

(3) interference with a specific assay by elevated triglycerides or with hydroxyurea therapy

(4) defective glucometer combined with failure to perform quality control


Features of falsified data about glucose control:

(1) glucose control logs suspicious

(1a) same ink used over weeks with less than expected variability in handwriting

(1b) no blood spots or smudges on the paper

(1c) nonrandom distribution in the recorded numbers (too many readings ending in the same number)

(1d) long periods with results in a narrow range, rather than showing expected variability

(2) unwillingness to produce logs

(3) having the patient use a glucometer meter with memory, then compare stored results with recorded logs

(4) discrepancy between the recorded use of insulin or testing supplies and purchase records with a pharmacy

(5) directly observe the patient in a controlled environment for several hours (This may be more effective in detecting factitious hypoglcyemia, since changes in hemoglobin A1c tend to reflect long term control. The method could help identify other discrepancies that would justify confrontation. There would be a discrepancy between the observed level of control and that shown on logs.)


Features of a hemoglobinopathy affecting the percent hemoglobin A1c:

(1) presence of an abnormal hemoglobin in the patient

(2) first degree relatives without diabetes mellitus show an elevated hemoglobin A1c level

(3) fructosamine values should be normal if there is good control

(4) if elevated hemoglobin F is identified, it may be necessary to use an affinity method or ion capture immunoassay rather than ion exchange elution.


Features of interference with the hemoglobin A1c assay:

(1) using an alternative method gives lower values

(2) evidence for elevated trigylcerides or history of hydroxyurea therapy

(3) fructosamine values may be normal if there is good control


Features of defective glucometer in combination with failure to perform quality control:

(1) failure to maintain monitor as instructed and to perform quality control

(2) simultaneous glucose testing between glucometer and an alternative method differ


To read more or access our algorithms and calculators, please log in or register.