The patient was a teenage African American female with a 2-week history of polyuria and polydipsia. There was no weight loss or nausea. She also presented with bilateral pain in her lower extremities and chest pain. During transit by EMS, her capillary glucose measured with a point-of-care device was 368 mg/dL.

These were her labs on admission:

Patient Result Reference Interval
Venous pH 7.26 7.3-7.4
Venous pCO2 23 mm Hg 42-53
Venous pO2 73 mm Hg 35-45
Venous HCO3- 10 meq/L 21-27
Venous base deficit 16 meq/L 0-3
Sodium 134 mmol/L 136-145
Potassium 4.1 mmol/L 3.3-5.1
Chloride 111 mmol/L 98-107
Carbon dioxide 8 mmol/L 22-30
Creatinine 0.62 mg/dL 0.40-1.10
BUN 6 mg/dL 6-20
Glucose 181 mg/dL 65-99
Urine glucose >1000 mg/dL Negative
Urine ketones >150 mg/dL Negative

More admission data:

Patient Result Reference Interval
WBC 20.50 K/uL 4.5-13.5K
Hemoglobin 9.9 g/dL 11.5-15.5
Hematocrit 28% 35-45
RBC count 3.16 million 4.0-5.2
MCV 87 fL 77-95
Red cell distribution width 16% 11-14
Corrected reticulocyte count 7.4% 0.5-1.8
Neutrophils 70% 40-80
Lymphocytes 18% 20-45
Monocytes 7% 2-10
Eosinophils 2% 0-8
Basophils 1% 0-2
Large unstained cells 3% 0-4
Platelet count 183 K/uL 150-450K

Hemoglobin A1c was requested and was measured at zero (0) percent. Below is the HPLC tracing.

Why wasn’t any A1c measured?

Answer

This patient had been previously diagnosed with hemoglobin SC (i.e., heterozygosity for hemoglobin S and hemoglobin C). The clinical presentation of chest and leg pain is consistent with a sickling crisis including the acute chest syndrome probably precipitated by fluid loss and acidosis caused by new-onset type 1 diabetes with ketoacidosis.

The CBC displayed anemia and the peripheral smear reported moderate anisocytosis and sickle forms. In the absence of hemoglobin A0, hemoglobin A1 can not detected by HPLC. Hemoglobin A1c could be measured by immunoassay. However, with shortened red blood cell survival from hemolysis, the A1c measured by immunoassay could be falsely low. This would also be true if total glycohemoglobin were measured.

The HPLC tracing displayed 52% hemoglobin S and 39% hemoglobin C. Hemoglobin F was elevated at 5.4%. A hemoglobin electrophoresis from 2 years earlier revealed: 48% hemoglobin S, 7% hemoglobin F and 46% hemoglobin C.