Protein S assays: an analysis of North American Specialized Coagulation Laboratory Association proficiency testing.
To assess current laboratory practice and the performance of different reagent-instrument combinations for protein S testing, protein S results from the North American Specialized Coagulation Laboratory Association (NASCOLA) proficiency testing surveys for 2002 and the first half of 2003 were analyzed. A written survey of NASCOLA laboratories also was performed to further assess current laboratory practices for protein S testing. The free protein S antigen assays and the Diagnostica Stago Staclot protein S assay were extremely accurate in detecting a heterozygous type I protein S deficiency. Another functional protein S assay and most total protein S assays were less reliable, depending to some extent on the instrument. All assays used by NASCOLA laboratories appropriately identified normal protein S specimens. NASCOLA laboratories performed at least as well as European Concerted Action on Thrombosis laboratories in the proficiency tests. The results suggest that the diagnosis of heterozygous protein S deficiency may be problematic with some currently available assays. Many total protein S antigen assays do not add to the diagnosis and can be unreliable for protein S deficiency subtyping. Better standardization of functional and antigenic assays is needed.
Division of Clinical Laboratories, Department of Pathology, Massachusetts General Hospital, Boston 02114, USA.
Elizabeth M
EM
Van Cott
Marlies
M
Ledford-Kraemer
Piet
P
Meijer
William L
WL
Nichols
Stephen M
SM
Johnson
Ellinor I B
EI
Peerschke
D001681:Biological Assay; D001777:Blood Coagulation; D019411:Clinical Laboratory Techniques / Q000592:standards*; D006801:Humans; D007753:Laboratories / Q000592:standards*; D009656:North America; D010338:Pathology, Clinical / Q000295:instrumentation / Q000379:methods / Q000592:standards; D017293:Protein S / Q000032:analysis*
D017293:Protein S