Diagnostic property of direct referral from general practitioners to contrast-enhanced thoracoabdominal CT in patients with serious but non-specific symptoms or signs of cancer: a retrospective cohort study on cancer prevalence after 12 months.

Objectives: To describe the diagnostic properties of thoracoabdominal contrast-enhanced CT (ceCT), when general practitioners (GPs) managed referral to ceCT through the non-specific symptoms or signs of cancer-cancer patient pathway (NSSC-CPP).

Design: Retrospective cohort study including patients from a part of Denmark.

Setting: Department of Internal Medicine at a university hospital.

Participants: In total, 529 patients underwent ceCT.

Primary And Secondary Outcomes: Our primary objective was to estimate the negative and positive likelihood ratios for being diagnosed with cancer within 1 year after ceCT. Our secondary outcomes were prevalence and final diagnoses of malignancy (including temporal trends since implementation of NSSC-CPP in 2012), the prevalence of revision of CT scans and referral patterns based on ceCT results.

Results: In total, 529 subjects underwent ceCT and malignancy was identified in 104 (19.7%) patients; 101 (97.1%) during initial workup and 3 patients during the subsequent 12 months follow-up.Eleven patients had a false-negative ceCT, and revision classified the ceCT as 'probable/possible malignancy' in eight (73%) patients. The negative predictive value was 98% and positive predictive value 63%. Negative and positive likelihood ratios for malignancy was 0.1 and 7.9, respectively.

Conclusion: Our study shows that ceCT as part of GP-coordinated workup has a low negative likelihood ratio for identifying malignancy; this is important since identifying patients for further workup is vital.