Tag Archives: ANCA

Serology Titers Associated with Clinical Expression of Ulcerative Colitis in Children

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Briefly noted: A recent study (EA Spencer et al.Inflamm Bowel Dis 2018; 24: 1335-42) examined phenotype and serology in 399 children with newly diagnosed ulcerative colitis (PROTECT study).

Key findings:

  • 65% had positive serology for pANCA; 62% in those <12 and 66% in those ≥12 years
  • 19% had positive serology for anti-CBir1; 32% in those <12 and 14% in those ≥12 years
  • High titer (≥ 100)) pANCA positivity was associated with more extensive disease but not with PUCAI values or Mayo endoscopic subscores.

My take: The serology titers for IBD, in my view, have academic interest but do not routinely enhance patient care.

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How helpful are serologies in pediatric inflammatory bowel disease?

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For quite some time, I have been unimpressed with the utility of serologies in distinguishing Crohn’s disease and Ulcerative Colitis.  While some of these tests claim some usefulness, when one excludes the obvious cases of Crohn’s disease (eg. perianal disease, fistulizing disease, small bowel disease), these claims seem quite dubious  Another study backs up my interpretation: L Birimberg-Schwartz et al. Inflamm Bowel Dis 2016; 22: 1908-14

This longitudinal report from the IBD Porto Group examined a multicenter retrospective cohort of 406 children with isolated colonic disease.  These children had a mean age of 10.5 years.  117 had Crohn’s colitis, 143 had ulcerative colitis, and 146 had IBD-unclassified (IBDU).

Key findings:

  • Among those with IBDU, the most prevalent serologic profile was pANCA neg/ASCA neg (41%).  34% had pANCA pos/ASCA neg, and 17% and pANCA neg/ASCA pos.
  • ANCA+: present in 43% of patients with IBDU, 64% of patients with UC, and 30% of patients with Crohn’s.
  • ASCA+ (IgA or IgG): present in 26% of  patients with IBDU, 6% of patients with UC, and 40% of patients with Crohn’s.
  • pANCA neg/ASCA pos did help differentiate Crohn’s colitis versus IBDU with 83% specificity, 96% positive predictive value; however the sensitivity was only 33% and the negative predictive value was only 13%.
  • pANCA neg/ASCA pos also differentiated Crohn’s colitis compared with ulcerative colitis with 97% specificity, and 90% positive predictive value however the sensitivity was only 33% and the negative predictive value was only 40%.
  • pANCA pos/ASCA neg did NOT differentiate well.  For IBDU versus UC, the specificity was 66%, the positive predictive value was 94%; the sensitivity was 65% and the negative predictive value was 38%.

In short, these tests generally have poor sensitivity.  If ASCA antibodies are present, which occurred in only 23%, the serology performs better but still usually not well-enough to help with big decisions. The presence of positive serology was associated with an increased likelihood of more severe disease.

Before you order IBD serology, you may want to consider whether you might use the money for this costly test in a better way.

My take (borrowed from authors): “Serology cannot routinely be recommended for differentiating between IBDU versus CC or UC as a sole diagnostic criterion given its low diagnostic utility.”

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Serology in IBD

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Serological antibodies against a number of antigens have shown some utility in differentiating inflammatory bowel disease (IBD) from non-IBD and in distinguishing Crohn’s disease (CD) from ulcerative colitis (UC).  A recent article evaluated 204 articles in a systematic review of these serological markers (Inflamm Bowel Dis 2012; 18: 1340-55).

The study has several useful tables and a long list of references.  In its Table 1, 10 serologies are listed with a range for prevalence in CD, UC, alternative GI conditions, and in healthy population.  Table 2 summarizes the data in terms of sensitivity, specificity, positive predictive value, negative predictive value for these antibodies in determining IBD from non-IBD.

With regard to specific antibodies, the review highlights 10 antibodies:

1. Anti-neutrophil cytoplasmic antibodies (ANCA).  Autoantibody directed against a constituent of neutrophil granules.  With IBD (especially UC), an atypical perinuclear (pANCA) staining pattern with indirect immunofluorescence and DNase-sensitive make this pattern different from ANCA due to vasculitis.

2-7. Anti-glycan antibodies –directed against cell wall microbes and reflect interaction between the immune system and glycosylated cell wall components of microbiota.

2. Anti-Saccharomyces cerevisiae (ASCA IgA and IgG) –antibodies directed against yeast cell wall.  While ASCA antibodies are commonly found in CD patients, 20-25% (or higher in some studies) of healthy relatives will test positive for these antibodies as well.  Approximately 6% of relatives of UC patients will be ASCA-positive.

3. Anti-laminaribioside carbohydrate IgG antibodies (ALCA) –antibodies directed against laminaribioside

4. Anti-chitobioside carbohydrate IgA antibodies (ACCA) –antibodies directed against chitobioside

5. Anti-mannobioside carbohydrate IgG antibodies (AMCA) –antibodies directed against mannobioside

6. Anti-L –antibodies directed against laminarin (large polysaccharide)

7. Anti-C –antibodies directed against chitin (large polysaccharide)

8. Anti-OmpC.  OmpC is a transport protein of E coli

9. Anti-I2.  I2 is a Pseudomonas-associated antigen

10. Anti-CBir1.  CBir1 is a bacterial flagellin antigen

Conclusions:

  • Serology has only limited value for the initial diagnosis of IBD.
  • Serology has ‘better value’ in differentiating CD from UC, though there is substantial variability in serologic responses in both diseases.  Probably, serology is most useful in unclassified IBD (IBD-U) in preoperative setting; serology may help predict risk of developing complications among patients undergoing pouch surgery.
  • Serology is useful in predicting a complicated disease course. The presence and magnitude of these antibodies are strong predictors of disease progression.

Additional references:

  • Pediatrics. 2010 Jun ;125 (6):1230-6.  Shortcomings of the inflammatory bowel disease Serology 7 panel. 
  • -Clin Gastro & Hep 2008; 6: 1105. Increased immune reactivity/markers associated with aggressive disease.
  • -IBD 2006; 12:1122. Expression of I2 antibodies (against a bacterial antigen of psedomonas fluorescens) was highly associated with clinical response to diversion. 15/16 with I2-pos had clinical response; 2/11 I2-neg had clinical response.
  • -IBD 2008; 14: S4 abstract 0010. Practical experience with IBD serology (n=90) much less accurate than reported by Prometheus: overall accuracy of 63% (vs 92%), 66% sensitivity (vs 93%), 59% specificity (vs 95%), 75% PPV (vs 96%), and 49% NPV (vs 90%). In this population, 34% of known IBD were incorrectly predicted. Of 32 who did not have any evidence of IBD after clinical investigation, 40% (13) were seropositive.
  • -Clin Gastro & Hep 2008; 6: 1105. Increased immune reactivity/markers associated with aggressive disease.
  • -IBD 2008; 14; 129. Serologic markers not very useful clinically.
  • -Pediatrics 2007; 119: e193. IBD serology performed poorly in comparison to combination of Hgb/ESR with regard to sensitivity (60% vs. 83%), specificity (92% vs. 96%), positive predictive value (60% vs. 79%) for IBD in children, n=227. Also one third of all positive serology in patients w/o IBD. The positive predictive value in patients w/o rectal bleeding was 35% vs 60% for routine tests.
  • -Gastroenterol 2006; 131: 366. antibodies against laminaribioside, chitobioside, and mannan have predictive value in detecting Crohn’s disease.
  • -Gastroenterol 2006; 130: 1078. Unaffected relatives positive for either OmpC or ASCA in 20% in large cohor (n=619 unaffected relatives. OmpC present in up to 44% of CD pts, up to 24% of UC pts, and 6% of controls.