Chapter 9:	Laboratory Test Data
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Hemoglobin (HGB), Total

This test evaluates the amount of hemoglobin found in a deciliter (100 ml) of whole blood. The purpose of HGB Total tests are to help calculate MCH, mean corpuscular hemoglobin concentrations, the severity of anemia or polycythernia, and assist monitoring of the patient’s subsequent response to therapy.

Values and Interpretation

Concentrations levels of hemoglobin can vary based on the patient’s age and sex, and type of blood sample drawn for testing. Low concentrations can be an indication of recent hemorrhages, anemia, or excessive retention of fluids, recent hemorrhage, or fluid retention. Elevated concentrations can indicate hemoconcentration from polycythemia or dehydration.

Hemoglobin Derivatives

Subsequent to the onset of signs of toxicity (i.e., anoxia and cyanosis), this test is used to calculate the percentage of total hemoglobin containing abnormal derivatives such as: carboxyhemoglobin, sulfhemoglobin, and methemoglobin. Normal concentrations include:

• Carboxyhemoglobin = 3% of the total hemoglobin (up to 15% in tobacco smokers)

• Methemoglobin = less than 3%

• Sulfhemoglobin = undetectable

Hematocrit (Hct)

The percentage (by volume) of packed red blood cells (RBCs) in a whole blood sample is measured by the Hct. Centrifugation of anticoagulated whole blood in a capillary tube causes the packing. The number of RBCs and the average size of the RBC affect hematocrit levels. Hct test results are utilized to calculate two erythrocyte indices: mean corpuscular volume (MCV), and mean corpuscular hemoglobin concentration (MCHC).

The purposes of Hct tests include:

• Facilitating diagnosis of hydration, polycythemia, and anemia

• Calculating red cell indices

• Monitor fluid imbalance, blood loss and replacement

• Performing screening when evaluating the complete blood count

Values and Interpretation

Factors affecting Hct values include: type of blood sample taken, patient’s sex and age, type of sample, and competency of the lab conducting the test. Reference values range from 40% to 54% for men, and 37% to 47% for women. Low Hct can result from anemia or hemodilution, while high Hct is suggestive of polycythemia or hemoconcentration.

Glucose, Fasting Blood Sugar (FBS)

The FBS test measures plasma glucose levels following a 12 to 14 hour fast. It is the test most often used to screen for diabetes mellitus. The purposes of FBS tests are:

• Screening for diabetes mellitus and other glucose metabolism disorders

• Monitoring drug or dietary therapy in diabetic patients

• Determining the insulin requirements in patients with uncontrolled diabetes mellitus, and those requiring parenteral or enteral nutritional support

• Evaluating patients with hypoglycemia

Values and Interpretation

While the normal range for FBS tests can vary depending on the particular lab procedure used, normal values after an 8-12 hour fast generally are:

• Fasting serum = 70 to 100 mg/dl or (3.9 to 5.6 mmol/L).

• Fasting whole blood = 60 to 100 mg/dl or (3.3 to 5.6 mmol/L).

• Nonfasting = 85 to 125 mg/dl or (4.7 to 6.9 mmol/L).

• In persons or patients with an average age 50 to 70 to 115 mg/dl or (3.9 to 6.4 mmol/dl) in persons under age 50.

If fasting blood glucose levels at or higher than 140 to 150 mg/dl (7.8 to 8.3 mmol/L) or higher are measured on two or more occasions, the patient may be considered to be diabetic if other causes of hyperglycemia have been ruled out. Nonfasting levels higher than 200 mg/dl (11. 1 mmol/L) are also suggestive of diabetes. Pancreatitis, recent acute illness (such as myocardial infarction), Cushing’s syndrome, pituitary adenoma, pancreatitis, hyperthyroidism, chronic hepatic disease, and pheochromocytoma can also cause elevated fasting blood glucose levels.

Depressed glucose levels can be caused by: hyperinsulinism, insulinoma, von Gierke’s disease, functional or reactive hypoglycemia, hypothyroidism, adrenal insufficiency, congenital adrenal hyperplasia, hypopituitarism, islet cell carcinoma of the pancreas, hepatic necrosis, and glycogen storage disease.