Fourth Reported Case of Hemoglobin South Florida: A Rare Hemoglobin Variant That Causes Falsely Elevated HbA1c Values
Bibliographic record
Abstract
We report a case of a rare hemoglobin (Hb) variant, Hb South Florida (Hb-SF) with only three cases reported worldwide to our knowledge since initial description in 1985. It causes falsely elevated glycosylated hemoglobin (HbA1c) results during standard laboratory testing in the range of poorly controlled diabetes mellitus. A 42-year-old woman with a history of sclerosing bone dysplasia was noted to have an elevated HbA1c (13.8%) during routine blood work using the ion-exchange high performance liquid chromatography (HPLC) method. The patient did not have a prior diagnosis of diabetes mellitus and denied any symptoms consistent with diabetes. Physical exam was unremarkable. Her blood sugars were normal to minimally elevated. Over several months, she was noted to have persistent elevation in HbA1c in the range of 12-14%. She remained asymptomatic. The patient was referred to endocrinology clinic. Hb electrophoresis was performed due to suspicion for a hemoglobinopathy. The patient was noted to be heterozygous for a rare Hb variant called Hb South Florida that causes falsely elevated HbA1c levels. Her corrected HbA1c, when evaluated by affinity column HPLC, was in normoglycemic range. Hb South Florida was first described in 1985 in Tampa Florida and has since been reported in two other cases worldwide. The Hb is not associated with any clinical disorder reported in literature. There are many commercially available tests for measuring HbA1c levels. Additionally, structural variants in Hb interfere with many of the methods. Ion-exchange HPLC separates Hb based on their charge differences. Hb South Florida variant substitutes a neutral amino acid for a charged one, with valine substituted by methionine. This alteration decreases the transit time in the ion exchange column and causes it to co-elute together with HbA1c, giving a falsely elevated value as they get measured as same species. Affinity chromatography is based on affinity of a species for a particular ligand. It recognizes the structure of the N-terminal glycated amino acids of the beta chain of Hb. In the case of Hb South Florida, it was able to separate the variant Hb from glycated species. This is the fourth case of Hb variant South Florida to our knowledge. It is important for clinicians to keep a wide perspective when making an assessment of diabetes solely based on HbA1c values. Patients who do not present with symptoms consistent with diabetes, and have normal blood glucose should prompt a further workup for abnormal Hb variants. This should be done in order to prevent incorrect diagnosis and treatment. J Med Cases. 2015;6(5):229-231 doi: http://dx.doi.org/10.14740/jmc2134w
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".