Lab Values

Common Lab Values Chart
BUN 8-22mg/dL
PT (Prothrombin Time)11-16 seconds
PTT (Partial thromboplastin time)25-38 seconds
INR (International Normalized Ratio)0.8-1.2
Platelet Count150,000-350,000µL
3.2-4.5 g/dL
Bilirubin 0.1-1.0 mg/dL
d-dimerNormal 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.