Lab Tests Diagnostic Medical Tests Medical Lab Tests
 Red BLOOD CELLS
 Red blood cell count
 Hematocrit
 Red cell indices
   Erythrocyte
 sedimentation rate
 Reticulocyte count
 Osmotic fragility
   HEMOGLOBIN
 Total hemoglobin
 Fetal hemoglobin
 Hemoglobin
 electrophoresis
 Sickle cell test
 Unstable hemoglobin
 Heinz bodies
   Iron and total
 iron-binding capacity
 Ferritin
 Methemoglobin
   WHITE BLOOD CELLS
 White blood cell count
   White blood cell
 differential
   PLATELET ACTIVITY
 Bleeding time
 Platelet count
 Capillary fragility
 Platelet aggregation
   COAGULATION
   Activated partial
 thromboplastin time
 Prothrombin time
 Activated clotting time
   One-stage factor
 assay:Extrinsic
 coagulation system
   One-stage factor
 assay:Intrinsic
 coagulation system
 Plasma thrombin time
 Plasma fibrinogen
 Fibrin split products
 Plasma plasminogen
 Protein C
 Euglobulin lysis time
 D-Dimer
   International
 normalized ratio

Home :: Hematocrit

Hematocrit (HCT) - Test

Also known as: Hct, Crit, Packed cell volume (PCV)

A hematocrit (HCT) test may be done separately or as part of a complete blood count. It measures percentage by volume of packed red blood cells (RBCs) in a whole blood sample; for example, an HCT of 40% indicates that a 100-ml sample of blood contains 40 ml of packed RBCs. Packing is achieved by centrifuging anti coagulated whole blood in a capillary tube so that red cells are tightly packed without hemolysis.

Purpose

  • To aid diagnosis of polycythemia, anemia, or abnormal states of hydration.
  • To aid calculation of two red cell indices: mean corpuscular volume and mean corpuscular hemoglobin concentration.

Patient preparation

  • Explain to the patient that HCT is tested to detect anemia and other abnormal blood conditions.
  • Tell him that a capillary blood sample will be taken. Explain who will perform the test and when.
  • If the patient is a child, explain to him (if he's old enough) and his parents that a small amount of blood will be taken from the finger or earlobe.
  • Inform the patient that food or fluids need not be restricted before the test.

Procedure and posttest care

  • Perform a finger stick, using a heparinized capillary tube with a red band on the anticoagulant end. Blood drawn from a capillary puncture has slightly lower HCT levels than blood drawn from a venipuncture.
  • Fill the capillary tube from the redbanded end to about two-thirds capacity, and seal this end with clay.
  • Alternatively, perform a venipuncture and fill a 7-ml lavender-top tube.
  • If a hematoma develops at the venipuncture site, apply warm soaks.
Precautions
  • Send the sample to the laboratory immediately.
  • If you perform the test, place the tube in the centrifuge with the red end pointing outward.
  • Fill the collection tube completely.
  • Invert the tube gently several times to mix the sample.

Reference values

HCT is usually measured electronically. The results are 3% lower than manual measurements, which trap plasma in the column of packed RBCs.
Reference values vary, depending on the type of sample, the laboratory performing the test, and the patient's age and sex, as follows:

  • neonates ages 0 to 2 weeks: 44% to 64%
  • infants ages 2 weeks to 2 months: 39% to 59%
  • infants ages 2 to 6 months: 35% to 49%
  • infants ages 6 months to I year: 29% to 43%
  • children ages 1 to 6: 30% to 40%
  • children ages 6 to 16: 32% to 42%
  • adult males: 42% to 52%
  • adult females: 36% to 48%.
Abnormal findings

Low HCT suggests anemia, hemodilution, or massive blood loss. High HCT Indicates polycythemia or hemoconcentration due to blood loss and dehydration.

Interfering factors

  • Failure to fill the tube properly, to use the proper anticoagulant, or to adequately mix the sample and the anticoagulant.
  • Hemolysis due to rough handling of the sample or drawing the blood through a small-gauge needle for venipuncture.
  • Hemoconcentration due to tourniquet constriction for longer than 1 minute (increase, typically 2.5% to 5%).
  • Drawing the blood from the same arm used for I. V. infusion.
  • Elevated blood glucose or sodium (possible increase due to erythrocyte swelling)
  • Hemodilution or dehydration.

Diagnostic Medical Tests
Medical Tests
Dagnostic Tests
Lab Tests

Contact us | Link to us | Lab tests
Resources - 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
(c)Copyright Diagnostic-medical-tests.com All rights reserved.

The information provided on this web site should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. We will not be liable for any complications, or other medical accidents arising from the use of any information on this web site.