title: Systematic review with meta-analysis: faecal occult blood tests show lower colorectal cancer detection rates in the proximal colon in colonoscopy-verified diagnostic studies.
abstract: BACKGROUND
  The performance of faecal occult blood tests (FOBTs) to screen proximally located colorectal cancer (CRC) has produced inconsistent results.
  
  
  OBJECTIVE
  To assess in a meta-analysis, the diagnostic accuracy of FOBTs for relative detection of CRC according to anatomical location of CRC.
  
  
  METHODS
  Diagnostic studies including both symptomatic and asymptomatic cohorts assessing performance of FOBTs for CRC were searched from MEDINE and EMBASE. Primary outcome was accuracy of FOBTs according to the anatomical location of CRC. Bivariate random-effects model was used. Subgroup analyses were performed to evaluate test performance of guaiac-based FOBT (gFOBT) and immunochemical-based FOBT (iFOBT).
  
  
  RESULTS
  Thirteen studies, with 17 cohorts, reporting performance of FOBT were included; a total of 26 342 patients (mean age 58.9 years; 58.1% male) underwent both colonoscopy and FOBT. Pooled sensitivity, specificity, positive likelihood ratio and negative likelihood ratio of FOBTs for CRC detection in the proximal colon were 71.2% (95% CI 61.3-79.4%), 93.6% (95% CI 90.7-95.7%), 11.1 (95% CI 7.8-15.8) and 0.3 (95% CI 0.2-0.4) respectively. Corresponding findings for CRC detection in distal colon were 80.1% (95% CI 70.9-87.0%), 93.6% (95% CI 90.7-95.7%), 12.6 (95% CI 8.8-18.1) and 0.2 (95% CI 0.1-0.3). The area-under-curve for FOBT detection for proximal and distal CRC were 90% vs. 94% (P = 0.0143). Both gFOBT and iFOBT showed significantly lower sensitivity but comparable specificity for the detection of proximally located CRC compared with distal CRC.
  
  
  CONCLUSIONS
  Faecal occult blood tests, both guaiac- and immunochemical-based, show better diagnostic performance for the relative detection of colorectal cancer in the distal colon than in the proximal bowel.
authors: School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, Hong Kong.|Stanley Ho Big Data Decision Analytics Research Centre, The Chinese University of Hong Kong, Shatin, Hong Kong.|Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: H W
authors: HW
authors: Hirai
authors: School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, Hong Kong.|Stanley Ho Big Data Decision Analytics Research Centre, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: K K F
authors: KK
authors: Tsoi
authors: School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: J Y C
authors: JY
authors: Chan
authors: Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.|Department of Medicine and Therapeutics, LKS Institute of Health Science, State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: S H
authors: SH
authors: Wong
authors: Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: J Y L
authors: JY
authors: Ching
authors: School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, Hong Kong.|Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: M C S
authors: MC
authors: Wong
authors: Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.|Department of Medicine and Therapeutics, LKS Institute of Health Science, State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: J C Y
authors: JC
authors: Wu
authors: Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.|Department of Medicine and Therapeutics, LKS Institute of Health Science, State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: F K L
authors: FK
authors: Chan
authors: Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.|Department of Medicine and Therapeutics, LKS Institute of Health Science, State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: J J Y
authors: JJ
authors: Sung
authors: Institute of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.|Department of Medicine and Therapeutics, LKS Institute of Health Science, State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Shatin, Hong Kong.
authors: S C
authors: SC
authors: Ng
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003106:Colon / Q000473:pathology*; D003113:Colonoscopy / Q000379:methods / Q000592:standards*; D015179:Colorectal Neoplasms / Q000097:blood / Q000175:diagnosis*; D055088:Early Detection of Cancer / Q000379:methods / Q000592:standards*; D005260:Female; D006138:Guaiac / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009780:Occult Blood
chemical_list: D006138:Guaiac