Diagnostic performance of FOB Gold® in symptomatic primary care patients

BackgroundFaecal immunochemical tests (FIT) detect and quantify faecal haemoglobin (f-Hb) to triage symptomatic primary care patients for the risk of colorectal cancer (CRC).MethodFIT was performed using FOB Gold® on a Siemens ADVIA Chemistry XPT analyser at Stepping Hill Hospital. Diagnostic accuracy was assessed by following up FIT results between June 2023 and June 2024. Results of ≥10 <i>μ</i>g of haemoglobin per gram of faeces (µg/g) were considered as positive. The FIT results were matched with data from the Somerset cancer register, concluding if patient had CRC or non-CRC findings.ResultsA total of 12,640 patients were included in this study. Colonoscopies (or contrast CT) were performed on 1476 patients with f-Hb results of ≥10 µg/g and on 617 patients with f-Hb <10 µg/g as the clinician had further concerns. A total of 98 cancers were found (89 had f-Hb ≥10 µg/g and 9 had f-Hb <10 µg/g). The remaining 10,547 with f-Hb <10 µg/g were considered as non-CRC due to lack of follow-up for >6 months. Using the 10 µg/g cut-off, FOB Gold® sensitivity for CRC was 90.8% and the specificity was 88.9%; the positive predictive value was 6.0% and the negative predictive value was 99.9%. The receiver operating characteristic curve had an area under the curve of 0.92 (95% CI 0.89 to 0.95).ConclusionFOB Gold® has comparable diagnostic performance for detecting CRC in symptomatic primary care patients as other FIT systems at 10 µg/g.