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17. Optimising the use of faecal calprotectin for early diagnosis of IBD in primary care

O.M. Demir1, Z. Ahmed1, R.P.H. Logan1, 1Kings College Hospital, Gastroenterology, London, United Kingdom

Background

Faecal calprotectin ELISA (FC) is an exquisitely sensitive and specific test of intestinal inflammation and may have a role in distinguishing early IBD from other GI disorders (IBS) presenting in primary care. Previous data has shown that diagnostic uncertainty for symptomatic patients with FC between 50–150 µg/g might be resolved by a strategy of repeat testing 6–8 weeks later. The AIM of this study was to evaluate the safety and diagnostic utility of this strategy in patients with elevated FC levels in primary care.

Methods

Study population: All patients with a FC results within the pathology faecal calprotectin data set from June 2009–2012 (n = 9123). Patient data were cross checked with electronic patient records, radiology (PACS), endoscopy and histology data sets for SnoMed CT codes for IBD (T655260, T67000–6893). Exclusion criteria: previous diagnosis of IBD, and aged <16 yr at study entry.

Results

Of 9123 results, 2663 (29%) were from primary care and met the inclusion criteria. 62% were female, median age 52 yr (range 18–88yr), 56% were <55 yr old, and diarrhoea (50%) was the most frequent indication for FC testing. 1710 (65%) had FC values <50 µg/g and were negative and not retested. 483 (18%) had FC values between 50–150 µg/g and 440 (17%) had FC values >150–3000 µg/g. In the latter population, there were 13 new diagnoses of IBD (9 female, 7 with UC), in whom mean FC increased from 933 to 1666 µg/g (sem ±200) (ns) on repeat testing prior to specialist referral. In contrast, FC values fell rapidly in 37 patients with presumed infectious enteritis: initial mean FC decreased from 682 to 53 µg/g (sem ±155) (p < 0.05). In 66 patients with minimally elevated FC levels (50–150 µg/g), none developed IBD during 2years follow up, and repeat FC testing showed a non-significant fall in FC from a mean 88 to 65 µg/g (sem ±5) (ns), with sub-group analysis suggesting regression towards the mean.

Table: Sensitivity and specificity of CDAI remission and CDAI moderate-to-severe disease activity to predict MH and CRP normalization in CD
 CDAI <150 (N = 136)
CDAI ≥150 (N = 52)
CDAI ≥220 (N = 27)
CDAI <220 (N = 161)
Complete MH72/136 (52.9%)8/27 (29.6%)
 Sensitivity/Specificity (%)80.0/34.791.1/19.4
CRP normalization (<0.5 mg/dL)88/136 (64.7%)13/27 (48.2%)
 Sensitivity/Specificity (%)81.5/4088.0/17.5
CRP normalization & MH54/136 (39.7%)6/27 (22.9%)
 Sensitivity/Specificity (%)84.4/33.990.6/16.9

Conclusion

These data demonstrate that, in primary care, a strategy of repeat FC testing facilitates the diagnosis of IBD and the distinction between IBD and infectious enteritis. These data also show that repeat FC testing in patients with minimally elevated FC values is a safe strategy for patients with FC values in the ‘grey-zone’.