Peihong Hsu

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.

Proficiency testing results for heparin-induced thrombocytopenia in north america.

Between 2010 and 2012, North American Specialized Coagulation Laboratory Association (NASCOLA) distributed five proficiency testing challenges to evaluate laboratory testing for heparin-induced thrombocytopenia (HIT). Results (n = 355) were submitted from 43 unique laboratories for 10 samples (3 positive, 2 weak positive, and 5 negative). The vast majority of results were from commercial enzyme-linked immunosorbent assay (ELISA) methods, predominantly polyvalent assays. Laboratories performed well in the classification of clear negative and positive samples. All results (100%) submitted for the five negative samples (n = 173) and 97% of immunological results submitted for the three positive samples (n = 105) were correctly classified (the incorrect responses were two borderline classifications and, from a gel-agglutination method, one negative classification). There was more difficulty in the classification of the two weak positive samples (n = 70). In one survey, 61% of results from the weak positive sample were classified as positive, while 21% were called negative, 16% were called borderline, and 2% were called inconclusive. In a second survey, 16% of results from the weak positive sample were called positive, while 56% were called negative, and 28% were called borderline. Significant interlaboratory variation was observed for ELISA results, with coefficients of variation of about 20 to 30%. We conclude that there is variability in HIT laboratory testing and that identification of weak positive samples can be challenging.

Protein S testing in patients with protein S deficiency, factor V Leiden, and rivaroxaban by North American Specialized Coagulation Laboratories

In 2010-2012, the North American Specialized Coagulation Laboratory Association (NASCOLA) distributed 12 proficiency testing challenges to evaluate laboratory testing for protein S (PS). Results were analysed to assess the performance of PS activity, PS free antigen, and PS total antigen testing. Statistical analysis was performed on the numeric results and qualitative classification submitted for each method. There were 2,106 total results: 716 results from PS activity assays, 833 results from PS free antigen assays, and 557 results from PS total antigen assays. The three assay types performed well in the classification of five normal samples and nine abnormal samples, although certain PS activity methods were more likely to classify normal samples as abnormal and one PS total antigen assay was more likely to classify abnormal samples as normal. PS activity methods were affected by interfering substances such as heterozygous or homozygous factor V Leiden mutation (underestimation) and the anticoagulant drug rivaroxaban (overestimation). In conclusion, NASCOLA laboratories using a variety of PS assays performed well in the classification of clearly normal and abnormal samples. Laboratories performing PS activity assays should be aware of potential interferences in samples positive for FV Leiden or containing certain anticoagulant medications.

Quality of factor XI activity testing in North American Specialized Coagulation Laboratories

The performance of factor XI activity (FXI) by laboratories in the North American Specialized Coagulation Laboratory Association proficiency testing program was analyzed.

Factor VII assay performance: an analysis of the North American Specialized Coagulation Laboratory Association proficiency testing results

The performance of factor VII (FVII) assays currently used by clinical laboratories was examined in North American Specialized Coagulation Laboratory Association (NASCOLA) proficiency tests. Data from 12 surveys conducted between 2008 and 2010, involving 20 unique specimens plus four repeat‐tested specimens, were analyzed. The number of laboratories per survey was 49–54 with a total of 1224 responses. Numerous reagent/instrument combinations were used. For FVII > 80 or <40 U/dL, 99.5% of results (859/863) were correctly classified by laboratories as normal/abnormal. Classification of specimens with 40–73 U/dL FVII was heterogeneous. Interlaboratory precision was better for normal specimens (coefficient of variation (CV) 10.7%) than for FVII<20 U/dL (CV 33.1%), with a mean CV of 17.2% per specimen. Intralaboratory precision for repeated specimens demonstrated no significant difference between the paired survey results (mean absolute difference 2.5–5.0 U/dL). For specimens with FVII >50 U/dL, among commonly used methods, one thromboplastin and one calibrator produced results 5–6 U/dL higher and another thromboplastin and calibrator produced results 5–6 U/dL lower than all other methods, and human thromboplastin differed from rabbit by +7.6 U/dL. Preliminary evidence suggests these differences could be due to the calibrator. For FVII <50 U/dL, differences among the commonly used reagents and calibrators were generally not significant.

Testing for dabigatran and rivaroxaban by clinical laboratories.

Rivaroxaban and dabigatran are among the newest anticoagulants, and measuring their concentration in patients is a new challenge for clinical laboratories. We analyzed data from the ECAT proficiency program to determine how well the assays are performing in clinical laboratories internationally. Most laboratories received a passing grade (Z score <3) for the results of their dabigatran and rivaroxaban testing. Failing Z scores were not associated with any particular method. With dabigatran, some homemade calibrators gave higher results than the commercially available calibrators. There were no significant differences among the instruments or the 5 reagents in use, but results showed inter‐laboratory variability that could have clinical significance. The 3 reagents with the lowest number of users had poor inter‐laboratory precision. Ten different anti‐Xa reagents were in use for rivaroxaban testing. One reagent gave lower results than other reagents at 100 ng/mL but not at 300 ng/mL. There were no significant differences among the different rivaroxaban calibrators or instruments. In conclusion, inter‐laboratory precision could be improved for both dabigatran and rivaroxaban assays. Homemade dabigatran calibrators differed from commercially available calibrators, and there was a statistically significant difference between some of the rivaroxaban reagents. About 10% of results received failing Z scores or passed but fell in a range that require the laboratory to investigate for bias or other inaccuracy in their method. Am. J. Hematol. 91:E464–E467, 2016.

Classical Hodgkin Lymphoma With Aberrant CD8 Expression: A Clinicopathologic Study of Five Cases

Hodgkin/Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (CHL) are of B-cell origin. In a small number of CHL cases, the tumor cells can express T-cell antigens. CD8 expression in this setting is extremely rare. We identified 5 cases of CHL with aberrant CD8 expression from our database. The patients included 3 men and 2 women with a median age of 33 years (range = 20-59 years). All the patients initially presented with lymphadenopathy and variable number of RS cells. Two cases were classified as mixed cellularity type that showed prominent vascular proliferation mimicking peripheral T-cell lymphoma. Two cases represented nodular sclerosis type. The tumor cells in all cases were positive for CD8 and negative for CD2, CD3, CD4, and CD7 and carried germline T-cell receptor genes. Molecular studies revealed T-cell receptor genes to be in germline configuration in 4 cases with available information. Given the morphologic overlap with peripheral T-cell lymphoma and the rarity of this type of CHL, identifying more cases will help our better understanding of this entity.