American Association for Clinical Chemistry
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By William Winter, MD
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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?

 
Response:
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.
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About the Author
William Winter, MD
William Winter, MD 
 
Additional Resources
 
HbA1c: An Overview of Current Analytical Testing Issues. CLN February 2011

ADA Endorses HbA1c for Diabetes Diagnosis. CLN February 2010

Expert Committee Endorses HbA1c Test for Diagnosing Diabetes. CLN August 2009