Is it okay to run lab tests for testosterone, progesterone, T3 (triiodothyronine), and Complete Blood Count (CBC) after 24 hours if the sample has been properly handled and stored?

Laboratory Testing After 24 Hours for Testosterone, Progesterone, T3, and CBC

Properly spun blood samples for testosterone, progesterone, and T3 testing can be run after 24 hours, but CBC testing after 24 hours is not recommended due to significant changes in cell parameters.

Stability of Hormone Tests vs. CBC

Hormone Tests (Testosterone, Progesterone, T3)

• Hormone tests performed on properly processed serum/plasma samples show better stability than cellular components
• For hormone testing:
  • Samples should be centrifuged as soon as possible after collection (ideally within 1 hour)
  • After centrifugation and separation, the serum/plasma should be stored at appropriate temperatures
  • Properly processed and stored samples can maintain stability for hormone testing beyond 24 hours

Complete Blood Count (CBC)

• CBC parameters show significant changes after 24 hours, even with proper storage 1, 2
• Research shows that after 24 hours:
  • White blood cell counts tend to increase with time
  • Red blood cell morphology changes
  • Mean cell volume (MCV) significantly increases (from 83.89 to 87.50 fmol/l) 1
  • Platelet counts and neutrophil percentages increase
  • Lymphocyte percentages decrease

Proper Specimen Handling Protocol

Collection and Initial Processing

1. Collect blood in appropriate tubes (sodium heparin for cellular tests, appropriate anticoagulant for hormone tests) 3
2. Process specimens as soon as possible after collection
3. Centrifuge samples properly to separate cells from plasma/serum
4. For hormone tests, transfer serum/plasma to appropriate storage tubes after centrifugation

Storage Requirements

• For hormone tests (testosterone, progesterone, T3):

  • Store separated serum/plasma at 4°C if testing will be performed within 24 hours
  • For longer storage, freeze at -20°C (up to 1 month) or -80°C (longer term) 3

• For CBC testing:

  • Perform testing within manufacturer's specified timeframe 3
  • Ideally perform CBC testing within 24 hours of collection 2
  • Refrigeration (4°C) provides better stability than room temperature storage 2

Quality Control Considerations

Specimen Rejection Criteria

• Reject specimens that are:
  • Hemolyzed or frozen
  • Visibly clotted
  • Improperly labeled or misidentified 4
  • Received beyond acceptable timeframes for the specific test

Documentation Requirements

• Document any deviations from standard processing protocols
• Note storage conditions and duration on test reports when processing is delayed
• Follow laboratory policies for specimen rejection when appropriate

Conclusion

While hormone tests (testosterone, progesterone, T3) may yield acceptable results after 24 hours if properly processed and stored, CBC results are significantly affected by storage beyond 24 hours. For optimal patient care and accurate results, CBC testing should be performed within 24 hours of collection, while hormone testing has greater flexibility if proper specimen handling protocols are followed.