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Test Code LAB301 Platelet Count

Testing Algorithm

If platelet count is <50 K/cumm then an IPF (immature platelet fraction) will be performed and reported at an additional charge

Performing Laboratory

St. Louis Children's Hospital - Hematology

Specimen Requirements

Patient Preparation: None

Container/Tube  
Preferred: Lavender-top (EDTA) tube
Acceptable: Lavender-top (EDTA) samplette/microtainer
Collection Volume: 

Vacutainer: 2.0 mL (minimum 0.5 mL)
Microtainer: Full tube (minimum 0.3 mL)                                               

Submission Container/Tube: If specimen is coming from outside facility, send whole blood in original collection container.
Special Instructions: Immediately invert tube gently 8-10 times after collection to ensure proper mixing of blood and anticoagulant (this will avoid specimen clotting). Do not overfill tube. Send to lab promptly. 

Sample Rejection

Mislabeled or unlabeled specimens

Clotted specimens

Logistics

Test Availability: Monday-Sunday
Cut-off time: None; performed as received
Turnaround Time: Same day; 30 minutes from receipt in performing lab

Reference Values

Reference Interval: Platelet count (all ages): 150,000-400,000 K/cumm

IPF (if applicable)
   <6 months: 1.5-7.0%
6 months-12 years: 1.1-5.0%
12-18 years: 1.6-6.5%
≥ 18 years: 1.6-10.1%                                                                          

Critical Value: 

Inpatient Plt:
   <18 years: <25,000 K/cumm  OR  >1,000,000 K/cumm
   ≥ 18 years: <20,000 K/cumm  OR  >1,000,000,K/cumm                        
Outpatient or ED patient Plt:
all ages: <50,000 K/cumm  OR  >1,000,000 K/cumm

All critical test results will be automatically called back initially and every 72 hours thereafter with the exception of outpatient or ED patient results, those will be called every time.

Methodology

Electronic resistance detection enhanced by hydrodynamic focusing

Limitations

  • Red cell fragments, microcytic RBCs or white cell cytoplasmic fragments may interfere with automated platelet counts.

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: DO NOT SPIN. Give specimen directly to Hematology bench
Processed Volume: minimum 0.3 mL whole blood
Analyte Stability:

Specimen Type Temperature Time
Whole Blood (unprocessed)  Ambient 24 hours
  Refrigerated     24 hours
  Frozen  unacceptable       

NOTE: refrigerated specimens must be warmed to room temperature before analysis. 

Test Classification and CPT Code

85595

85055 - IPF (if applicable)

LOINC

plt: 777-3

IPF (if applicable): 71693-6

Last Reviewed

07/2025