Positive predictive values of ≥5% in primary care for cancer: systematic review

Background The positive predictive value (PPV) for cancer of symptoms, signs, and non-diagnostic test results of patients routinely consulting a GP (unselected primary care populations) can help to determine when malignancy should be excluded. Comparisons with other illness indicate that a value of 5% or more may be regarded as highly predictive.

Aim To identify symptoms, signs, and non-diagnostic test results in unselected primary care populations that are highly predictive of cancer.

Design of study Systematic review.

Setting Primary care.

Method Fourteen bibliographic databases were searched, using terms for primary care, cancer, and predictive values. Reference lists of relevant papers were hand-searched. Data were extracted and the quality of each paper was assessed using predefined criteria, and checked by a second reviewer.

Results Twenty-five studies were identified. PPVs of 5% or more in specific age and sex groups were reported for: rectal bleeding, change in bowel habit, and iron deficiency anaemia and colorectal cancer; haematuria and urological cancer; malignant rectal examination and prostate cancer; haemoptysis and lung cancer; dysphagia and oesophageal cancer; breast lump and breast cancer; and postmenopausal bleeding and gynaecological cancer.

Conclusion Robust evidence was found for eight symptoms, signs, and non-diagnostic test results as strongly indicative of cancer for specific age and sex groups in unselected primary care populations. These have the potential to improve the early diagnosis of some cancers in primary care by the use of computer warning flags, improved guidelines, audit, and appraisal.