Value of symptoms and additional diagnostic tests for colorectal cancer in primary care: systematic review and meta-analysis

Abstract

Objective: To summarise available evidence on diagnostic tests that might help primary care physicians to identify patients with an increased risk for colorectal cancer among those consulting for non-acute lower abdominal symptoms.

Data sources: PubMed, Embase, and reference screening. Study eligibility criteria Studies were selected if the design was a diagnostic study; the patients were adults consulting because of non-acute lower abdominal symptoms; tests included signs, symptoms, blood tests, or faecal tests. Study appraisal and synthesis methods Two reviewers independently assessed quality with a modified version of the QUADAS tool and extracted data. We present diagnostic two by two tables and pooled estimates of sensitivity and specificity. We refrained from pooling when there was considerable clinical or statistical heterogeneity.

Results: 47 primary diagnostic studies were included. Sensitivity was consistently high for age >or=50 (range 0.81-0.96, median 0.91), a referral guideline (0.80-0.94, 0.92), and immunochemical faeces tests (0.70-1.00, 0.95). Of these, only specificity of the faeces tests was good. Specificity was consistently high for family history (0.75-0.98, 0.91), weight loss (0.72-0.96, 0.89), and iron deficiency anaemia (0.83-0.95, 0.92), but all tests lacked sensitivity. None of these six tests was (sufficiently) studied in primary care.

Conclusions: Although combinations of symptom and results of immunochemical faeces tests showed good diagnostic performance for colorectal cancer, evidence from primary care is lacking. High quality studies on their role in the diagnostic investigation of colorectal cancer in primary care are urgently needed.

Fig 1 Results of search strategy and selection procedure

Fig 2 Risk of colorectal cancer in patients aged ≥50 (positive predictive value) versus risk in patients <50 (1−negative predictive value)

Fig 3 Risk of colorectal cancer in patients with rectal bleeding (positive predictive value) versus risk in those without rectal bleeding (1−negative predictive value); all studies conducted in secondary care

Fig 4 Risk of colorectal cancer in patients with rectal bleeding/dark blood (positive predictive value) versus risk in those without rectal bleeding/dark blood (1−negative predictive value)

Fig 5 Risk of colorectal cancer in patients reporting change in bowel habit (positive predictive value) versus risk in patients not reporting this symptom (1−negative predictive value)

Fig 6 Risk of colorectal cancer in patients meeting two week referral rule (positive predictive value) versus risk in those not meeting two week referral (1−negative predictive value)

Fig 7 Risk of colorectal cancer in patients with iron deficiency anaemia (positive predictive value) versus risk in patients without (1−negative predictive value)

Fig 8 Risk of colorectal cancer in patients with positive guaiac based faecal occult blood test result (positive predictive value) versus risk in patients with negative result (1−negative predictive value)

Fig 9 Risk of colorectal cancer in patients with positive immunochemical based faecal occult blood test result (positive predictive value) versus risk in patients with negative results (1−negative predictive value). All studies were conducted in secondary care. HbAb=haemoglobin-albumin complex, HbHp=haemoglobin-haptoglobin complex