What causes platelet count variation among hema analyzers??
Factors causing platelet count variation among hema analyzers - patient population ( Cancer vs non cancer patients), sample selection ( EDTA use - platelet clumps),reference method (flow cytometry vs impedance, light scatter method).
Remember different laboratories uses different hema analyzers and even if they're using the same machine platelet clumping differs per specimen collection
Platelet clumping is usually flagged by hema analyzers:
Platelet flags occurs when the analyzer detects the ff :1) RBC 2)Leukocyte fragments. It selects samples with platelet counts between 75 to 150 x 10 9.
Regarding platelet flags the best way to confirm them is using manual method (draw back: inter observer variability) or do a repeat extraction.
Here is a study done by Dr Sandhaus ( Cleveland University Hospital) published at the American Society of Clinical Pathology 2002. It compared platelet flags reported by 3 Hema analyzers (Sysmex, Coulter and Advivia) and it was rechecked manually to confirm their sensitivity and specificity.
Low
platelet count sensitivity and specificity in 3 different hema analyzers
1) Sysmex -Platelet clumps flag – 20 samples
True positive (with real platelet clumping when inspected manually) 4/20
False positive ( w/o any platelet clumping) 16/20
2) Coulter LH750 - Platelet clumps flag – 3 samples
True
positive (with real platelet clumping when inspected manually) 2/3
False
positive ( w/o any platelet clumping) 1/3
3) Advia 120 - Platelet clumps flag – 4 samples
True
positive (with real platelet clumping when inspected manually) 3/4
False
positive ( w/o any platelet clumping) 1/4
HENCE , OUT OF 27 REPORTED " LOW PLATELET COUNT " RESULTS - 18 TURNED OUT TO BE NORMAL (66% ERROR).
TAKE HOME MESSAGE: ALWAYS DOUBLE CHECK PLATELET CLUMPS IT OCCURS 10% OF THE TIME WHETHER BLOOD IS DRAWN VIA VENOUS OR CAPILLARY ROUTE.
Categories: Hematology:Platelet count
Tags: Platelet count CBC Hema analyzers
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