Factor XIII Assays and associated problems for laboratory diagnosis of factor XIII deficiency: an analysis of International Proficiency testing results.
We analyzed results from the External quality Control of diagnostic Assays and Tests program to assess current clinical laboratory practice and performance of different methods for factor XIII (FXIII) testing internationally. FXIII proficiency testing data from all eight surveys conducted in 2010 and 2011 were analyzed (1,283 results), comparing the three available methods for detecting FXIII deficiency, thus including clot-solubility qualitative activity, quantitative activity, and antigen. Clot-solubility qualitative assays detected a deficiency in only 16% (11/69) of samples with less than 2% FXIII. Assays using added thrombin detected more deficiencies (33%) than did assays without added thrombin (11%). The most commonly used quantitative activity method tended to produce higher results for low FXIII samples than other quantitative activity methods. Antigen results generally showed good accuracy compared with expected levels. The mean interlaboratory coefficients of variation showed wide variability, especially for samples with less than 10% FXIII activity. Laboratory self-classification of results (as normal vs. abnormal) was good, and was slightly better for specimens with ≤ 25% FXIII than for specimens with 26 to 70% or those with >70% FXIII. We conclude that quantitative activity assays perform better for detecting FXIII deficiency than clot solubility assays, although some quantitative activity assays overestimate low FXIII levels.
Department of Pathology/Laboratory Medicine, Hofstra North Shore-LIJ School of Medicine, Lake Success, New York.
Peihong
P
Hsu
Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota.
Nicole D
ND
Zantek
ECAT Foundation, Leiden, The Netherlands.
Piet
P
Meijer
Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada.
Catherine P M
CP
Hayward
Department of Pathology/Laboratory Medicine, Hofstra North Shore-LIJ School of Medicine, Lake Success, New York.
Judith
J
Brody
Department of Pathology/Laboratory Medicine, Hofstra North Shore-LIJ School of Medicine, Lake Success, New York.
Xinmin
X
Zhang
Department of Pathology and ARUP Institute for Clinical and Experimental Pathology, ARUP Laboratories, University of Utah, Salt Lake City, Utah.
Kristi J
KJ
Smock
Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts.
Elizabeth M
EM
Van Cott
D019411:Clinical Laboratory Techniques / Q000379:methods / Q000592:standards*; D005176:Factor XIII / Q000032:analysis*; D005177:Factor XIII Deficiency / Q000097:blood* / Q000175:diagnosis*; D006801:Humans; D007391:International Cooperation; D059021:Laboratory Proficiency Testing / Q000379:methods / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D005176:Factor XIII