BACKGROUND: Antibodies against tissue transglutaminase (TTG) of isotype IgA (IgA-aTTG) represent reliable diagnostic markers to confirm or exclude celiac disease (CD). Hemolysis (HL) is an important pre-analytical factor. HL can be quantified as HL index (HI) correlating with the concentration of free hemoglobin. TTG is abundant in erythrocytes and released upon HL. In immunoassays, the released TTG may interfere with binding of IgA-aTTG to the coated TTG. METHODS: We selected 17 HL-free sera from children with biopsy-confirmed CD: 7 with low-positive (1-5 multiples of upper limit of normal [×ULN]), 5 with intermediate (5-10 × ULN) and 5 with high IgA-aTTG (10-15 × ULN). Sera were spiked with hemolysates resulting in HIs ranging from 12.5 to 800 (12.5-800 mg/dL free hemoglobin). RESULTS: IgA-aTTG values were significantly decreased (>10%) after addition of hemolysates even if HL was invisible (HI <50). This effect is diagnosis-relevant if IgA-aTTG values are measured just below the cut-offs: (i) 0.4-1 × ULN at HI ≥25 (CD not excludable) and (ii) 8.5-10 × ULN at HI ≥200 (diagnosis of CD without biopsy not possible). Antibodies against deamidated gliadin were not influenced by HL. CONCLUSIONS: IgA-aTTG results in sera with HI ≥25 can yield inconclusive results. Therefore, those antibody results should be assessed only under consideration of the HI.
BACKGROUND: Antibodies against tissue transglutaminase (TTG) of isotype IgA (IgA-aTTG) represent reliable diagnostic markers to confirm or exclude celiac disease (CD). Hemolysis (HL) is an important pre-analytical factor. HL can be quantified as HL index (HI) correlating with the concentration of free hemoglobin. TTG is abundant in erythrocytes and released upon HL. In immunoassays, the released TTG may interfere with binding of IgA-aTTG to the coated TTG. METHODS: We selected 17 HL-free sera from children with biopsy-confirmed CD: 7 with low-positive (1-5 multiples of upper limit of normal [×ULN]), 5 with intermediate (5-10 × ULN) and 5 with high IgA-aTTG (10-15 × ULN). Sera were spiked with hemolysates resulting in HIs ranging from 12.5 to 800 (12.5-800 mg/dL free hemoglobin). RESULTS:IgA-aTTG values were significantly decreased (>10%) after addition of hemolysates even if HL was invisible (HI <50). This effect is diagnosis-relevant if IgA-aTTG values are measured just below the cut-offs: (i) 0.4-1 × ULN at HI ≥25 (CD not excludable) and (ii) 8.5-10 × ULN at HI ≥200 (diagnosis of CD without biopsy not possible). Antibodies against deamidated gliadin were not influenced by HL. CONCLUSIONS:IgA-aTTG results in sera with HI ≥25 can yield inconclusive results. Therefore, those antibody results should be assessed only under consideration of the HI.
Authors: Johannes Wolf; Norman Haendel; Johannes Remmler; Carl Elias Kutzner; Thorsten Kaiser; Thomas Mothes Journal: J Clin Lab Anal Date: 2017-11-23 Impact factor: 2.352
Authors: Johannes Wolf; David Petroff; Thomas Richter; Marcus K H Auth; Holm H Uhlig; Martin W Laass; Peter Lauenstein; Andreas Krahl; Norman Händel; Jan de Laffolie; Almuthe C Hauer; Thomas Kehler; Gunter Flemming; Frank Schmidt; Astor Rodrigues; Dirk Hasenclever; Thomas Mothes Journal: Gastroenterology Date: 2017-04-28 Impact factor: 22.682
Authors: Johannes Wolf; Annika Jahnke; Kai Fechner; Thomas Richter; Martin W Laass; Almuthe Hauer; Martin Stern; Jan de Laffolie; Gunter Flemming; Thomas Mothes Journal: Clin Chim Acta Date: 2016-06-23 Impact factor: 3.786
Authors: Johannes Wolf; Norman Haendel; Johannes Remmler; Carl Elias Kutzner; Thorsten Kaiser; Thomas Mothes Journal: J Clin Lab Anal Date: 2017-11-23 Impact factor: 2.352