Lab Values

Common Lab Values Chart
BUN	8-22mg/dL
Creatinine	0.6-1.2mg/dL
PT (Prothrombin Time)	11-16 seconds
PTT (Partial thromboplastin time)	25-38 seconds
INR (International Normalized Ratio)	0.8-1.2
Platelet Count	150,000-350,000µL
Albumin	3.2-4.5 g/dL
Bilirubin	0.1-1.0 mg/dL
d-dimer	Normal range varies

The lab values listed in the figure above are important for a CT Technologist to know and understand. The ability for a patient to receive iodinated contrast will depend directly on these values.
A patient’s renal function is indicated by the levels of blood urea nitrogen (BUN) and creatinine present. These levels can be examined either as a ratio or individually.
- Normal BUN values in adults range from 8 to 22 mg/dL
  - By itself, BUN is not a sufficient indicator of renal insufficiency.
- Normal creatinine levels range from 0.6-1.2 mg/dL
A more accurate measure of renal function is GFR (Glomerular filtration rate). eGFR (estimated GFR) is an estimation of the rate in which the bloodstream filters creatinine.

To calculate eGFR the following is needed
- Patient’s measured serum creatinine level.
- Patient’s age, sex, and race.
Normal kidney function as determined by eGFR is a measurement greater than 90, but is often displayed as >60.
Abnormal or decreasing kidney function is shown by an eGFR measurement lower than the normal range, but is often displayed as a number <60.

Blood coagulation is measured by PT or Prothrombin time.
- To measure PT, a protein called tissue factor is added to the blood sample.
- 11 to 16 seconds is normal range for PT.
INR (international normalized ratio) is calculated to help standardize PT results. This is done because there can be differences in the batches of tissue factor as they are manufactured.
- The PT result is compared with a control sample using the INR.
- 0.8-1.2 is normal range for INR.
- Abnormalities in blood clotting are detected by PTT (Partial thromboplastin time).
  - 25 to 38 seconds is normal range for clotting time.
- Clotting ability is determined by platelet count.
  - 150,000-350,000µL of blood is normal platelet count.
- Deep vein thrombosis and pulmonary embolisms may be detected through d-Dimer testing. An elevated d-Dimer in the bloodstream can indicate fragmented protein in the blood, from the breaking down of blood clots. A CT Pulmonary Angiography may be performed of the pulmonary arteries if the d-Dimer value is elevated.
- To screen liver damage, an LFT (liver function test) is performed.
  - To perform an LFT, a panel of blood tests that measure different enzymes and proteins in the blood as it is circulating is run.