Fecal Immunochemical Test (FIT) for Colon Cancer Screening: Variable Performance with Ambient Temperature

Abstract

Introduction Fecal immunochemical tests (FITs) are widely used in colorectal cancer (CRC) screening, but hemoglobin degradation, due to exposure of the collected sample to high temperatures, could reduce test sensitivity. We examined the relation of ambient temperature exposure with FIT positivity rate and sensitivity. Methods This was a retrospective cohort study of patients 50 to 75 years in Kaiser Permanente Northern California’s CRC screening program, which began mailing FIT kits annually to screen-eligible members in 2007. Primary outcomes were FIT positivity rate and sensitivity to detect CRC. Predictors were month, season, and daily ambient temperatures of test result dates based on US National Oceanic and Atmospheric Administration data. Results Patients (n =472,542) completed 1,141,162 FITs. Weekly test positivity rate ranged from 2.6% to 8.0% (median, 4.4%) and varied significantly by month (June/July vs December/January rate ratio [RR] =0.79, 95% confidence interval [CI], 0.76 to 0.83) and season. FIT sensitivity was lower in June/July (74.5%; 95% CI, 72.5 to 76.6) than January/December (78.9%; 95% CI, 77.0 to 80.7). Conclusions FITs completed during high ambient temperatures had lower positivity rates and lower sensitivity. Changing kit design, specimen transportation practices, or avoiding periods of high ambient temperatures may help optimize FIT performance, but may also increase testing complexity and reduce patient adherence, requiring careful study.

Positive predictive values of fecal immunochemical tests used in the STOP CRC pragmatic trial

“…Several patient factors have been associated with FIT positivity and false positivity. In our analysis, women with a FIT‐positive result were about 50% more likely to have no evidence of advanced neoplasia than FIT‐positive men, which is similar to previous reports . Although other studies have reported no sex differences in FP, sex‐specific hemoglobin concentration cutoffs have been suggested.…”

“…In our analysis, women with a FIT-positive result were about 50% more likely to have no evidence of advanced neoplasia than FIT-positive men, which is similar to previous reports. 39,40 Although other studies have reported no sex differences in FP, 21,23 sex-specific hemoglobin concentration cutoffs have been suggested. In a large study that evaluated PPV for advanced neoplasia at varying hemoglobin concentration cutoffs, the PPVs achieved for women (33%-43%) were lower than for men (53%-63%) at every hemoglobin cutoff.…”

Accuracy of a fecal immunochemical test according to outside temperature and travel time

“… 13 Thus, some decrease in sensitivity and an increase in specificity of FIT when returned at high temperatures were expected. Several previous population-based studies investigated the association between ambient temperatures and positivity, but not sensitivity and specificity of FIT, 6 , 9 – 12 , 14 and most of them found a negative association between higher temperatures and FIT positivity. The largest study, 6 with nearly 200,000 evaluated FITs conducted in Florence, Italy, indicated that a 1°C increase in temperature decreased FIT positivity by 0.7% and that detection rates for AN were by 13% lower in summer than in winter.…”

“…Only at even higher temperature ranges (26.1–35.0°C and >35°C), positivity decreased strongly, by 22% and 41%, respectively. A study from California 12 (N=472,542) found differences in FIT positivity by month, with higher positivity rates during the winter months. Absolute differences in sensitivity of detecting CRC (estimated by record linkage with cancer registry data rather than by comparison with colonoscopy results) were small, however, ranging from 75% in June/July to 79% in December/January.…”

Bread and Butter of Family Medicine: Guidelines, Population Screening, Diagnostic Evaluations, and Practice Models

“…By looking at over 1.1 million mailed Fecal Immunochemical Tests, Doubeni et al 5 found that the sensitivity of the test varies with seasonal temperature changes. The authors discuss some interesting implications of this discovery as it applies to the planning and execution of population-based colorectal cancer screening programs.…”