Result card

  • EFF20: What is the accuracy of FIT for CRC screening against reference standard?
English

What is the accuracy of FIT for CRC screening against reference standard?

Authors: Jesús González-Enríquez, Francesca Gillespie, Stefania Lopatriello, Iñaki Imaz

Internal reviewers: Pseudo125 Pseudo125

We used both basic search done for the whole project and domain search (described in the Domain Methodology section). Furthermore test accuracy issues relative to Research Questions EFF 20, EFF 22, EFF 24, EFF 26, EFF 28, EFF 30 were selected from the above mentioned searches.

Inclusion criteria where: studies that report data on accuracy measures (sensitivity, specificity, positive and negative predictive values, likelihood ratios, SROC and other measures, detection rates), publication date after year 2000, FIT compared with gFOBT or alone, on asymptomatic average risk patients, age 50+ years, data on specific issues relative to selected research questions. Two investigators independently reviewed the titles and abstract. Disagreement was resolved by discussion. See Table 8 {EFF Appendix 3} for included articles. These articles were used, where pertinent, to answer all the above-mentioned Research Questions.

The quality assessment criteria for studies we used for all above mentioned Research Questions are R-AMSTAR {2}  {EFF Appendix 2} for systematic reviews and Cochrane risk of bias for observational studies {1}. Two independent reviewers assessed quality and bias. Disagreement was resolved by discussion.

Extraction tables where tailored to research questions issues. Articles covered by systematic reviews that were in our included list were not extracted.

Data was synthesized in tables were possible and research questions were answered starting from the best quality of available evidence.

Very few good quality diagnostic studies comparing FIT versus gFOBT use as reference standard colonoscopy or flexible sigmoidoscopy for all positive or negative results in the index test {10,15}.

Allison et al. {14} and Park et al. {13} studied participants that would receive screening in practice. The reference standards used for each study were different, with Allison et al comparing FIT with gFOBT, and with Park et al comparing FIT with colonoscopy. In both studies, the reference standard and the index test were performed in a short time. In Allison et al, colonoscopy was not used as the comparator to FIT, although participants with a positive test were referred for colonoscopy, and those with a negative test were referred for FS. In Park et al, FIT results were compared directly with colonoscopy results. The index test was independent of the reference standard used.

In the study conducted by Park et al, positivity was slightly higher for FIT (11.2%) than for gFOBT (7.9%), but this difference was not statistically significant. The sensitivity for detecting CRC was statistically significantly increased when using FIT compared with gFOBT (FIT 92.3% versus gFOBT 30.8% [P<0.01]). The sensitivity of FIT (33.9%) compared with gFOBT (13.6%) for detecting advanced adenoma (AA) was significantly higher (P<0.05).

The difference in specificity for both CRC and AA was not statistically significant when comparing FIT (CRC 90.1%; AA 90.6%) with gFOBT (CRC 92.4%; AA 92.4%). The difference in PPV for both CRC and AA was not statistically significant when comparing FIT (CRC 12.8%; AA 23.3%) with gFOBT (CRC 6.7%; AA 13.1%).

In the study conducted by Allison et al, positivity was statistically significantly lower for FIT than the sensitive gFOBT used in the study (FIT 3.2% versus gFOBT 10.1% [P<0.01]). The difference in sensitivity for detecting CRC and AA was not statistically significant for FIT (CRC 81.8%; AA 29.5%) compared with gFOBT (CRC 64.3%; AA 41.3%).The specificity for both CRC and AA was statistically significantly higher for FIT than for gFOBT (CRC FIT 96.9% versus gFOBT 90.1% [P<0.01]; AA FIT 97.3% versus gFOBT 90.6% [P<0.01]). The PPV for both CRC and AA was also statistically significantly higher for FIT compared with gFOBT (CRC FIT 5.2% versus gFOBT 1.5% [P<0.01]; AA FIT 19.1% versus gFOBT 8.9% [P<0.01]). Positive likelihood ratio for distal cancer was 26.7 (95% CI 19.4-36.6) with FIT and 6.5 (4.3-9.6) with gFOBT. Positive likelihood ratio for distal adenomas ≥1 cm was 11.0 (7.9-15.3) with FIT and 4.4 (3.5-5.5) with gFOBT. This measure summarizes how many times more likely patients with the disease will test positive compared with patients without the disease.

In summary, the sensitivity and PPV of FIT for detecting CRC and AA compared with a standard gFOBT is superior. Differences on specificity are not so relevant. Positivity rates for FIT using the manufacturer’s standard cut-off level in hemoglobin concentration are higher than for gFOBT.

In a review and meta-analysis {10} seven diagnostic cohort studies in diagnostic patients scheduled for colonoscopy are included. The pooled PPV for detecting advanced colorectal neoplasm was significantly higher for FIT than for gFOBT (0.41 vs 0.29, P < 0.01). The sensitivity of FIT (0.67, 95% CI 0.61–0.73) was superior to that of gFOBT (0.54, 95% CI 0.48–0.60), as were the specificities (0.85, 95% CI 0.83–0.87 vs 0.80, 95% CI 0.78–0.82). Figure shows the SROC for FOBT in diagnosing advanced colorectal neoplasm of diagnosed patients, which indicates the mildly higher diagnostic accuracy of FIT.

10936.EFF-20 Figure 1

Figure 1. Summary receiver operating characteristic curve (SROC) showing the diagnostic precision of guaiac-based fecal occult blood test (gFOBT) as Area Under the Curve (AUC) 0.7677, was lower than that of immunochemical fecal occult blood (iFOBT) as AUC 0.8241, for detecting advanced colorectal neoplasm in patients scheduled for colonoscopy.

From: Zhu MM, Xu XT, Nie F, Tong JL, Xiao SD, Ran ZH. Comparison of immunochemical and guaiac-based fecal occult blood test in screening and surveillance for advanced colorectal neoplasms: A meta-analysis.  Journal of Digestive Diseases, 2010; 11 (3): 148-60. 

Important
Partially
González-Enríquez J et al. Result Card EFF20 In: González-Enríquez J et al. Clinical Effectiveness In: Jefferson T, Cerbo M, Vicari N [eds.]. Fecal Immunochemical Test (FIT ) versus guaiac-based fecal occult blood test (FOBT) for colorectal cancer screening [Core HTA], Agenas - Agenzia nazionale per i servizi sanitari regionali; 2014. [cited 16 June 2021]. Available from: http://corehta.info/ViewCover.aspx?id=206

References