Factor

Results

Conclusions

Reference

Round of detection

A significant decrease was observed in the PPV for advanced neoplasia between the first and second round, from 55% (132/239) to 44% (112/252; P=.017). The PPV for CRC was 8% (20/239) in the first round versus 4% (9/252) in the second round (P=.024). Ten interval cancers were diagnosed.

Despite a significant decrease in the PPV for CRC in a second round of screening, a substantial number of significant lesions are detected in a second screening round. This applies more to advanced adenomas than to cancer cases and appears to be independent of the type of test used in the first round (guaiac FOBT or FIT).

Denters 2012{28}

Temperature

The mean log10 Hb concentration in the low temperature group was significantly higher than those in the high temperature group (0.36 vs. 0.25 ng/ml, p=0.000).

An increase in temperature of 1°C reduced the probability of a positive FIT by 3.1 %, but with no effect on  detection rate of colorectal neoplasms. High ambient temperature was not a significant risk factor for either the positive FIT result or the detection of colorectal neoplasms. Nevertheless, other Authors* reported   the FIT positive rate was significantly lower in summer than in winter, and explained these results as a decrease in fecal hemoglobin values in summer.

Potential instability of fecal hemoglobin at high ambient temperatures should be considered; however, its influence on performance of FIT may be attenuated by the short exposure time of fecal samples to high ambient temperature (i.e., rapid return system).

Cha 2012{29}

Delay between fecal

sampling and delivery at the laboratory

Delay in sample return increased false negative immunochemical FOBT’s. Mainly precursor lesions, but also colorectal cancer, will be missed due to delayed sample return.  The decreased performance of the FIT due to delayed return of the sample was observed to be independent of the cut-off value for positivity of the FIT.

Although selection bias could in a certain measure result in a false negative result,  The evidence in this study shows how important it is to control all aspects and logistics of screening protocols. Subjects invited for screening should be adequately informed of the necessity of prompt return of the sample and reporting the date of taking the sample. However, more complicated information and effort, as well as the pressure of prompt return, might also result in decreased participation. The production of a less sensitive hemoglobin stabilizing buffer with improved stability is suggested. Until a less sensitive hemoglobin stabilizing buffer is produced, monitoring delay between fecal sampling and laboratory research should be part of quality control for screening with immunochemical FOBT. Inviting participants to perform a second test when delay is 5 days or more could be considered.

Van Rossum 2009{30}

Diet restrictions

The restricted diet subgroup and unrestricted diet subgroup had showed significant difference for

advanced neoplasm detection rate and compliance rate

FIT removes the need for dietary restrictons.

However, some FIT advised alcohol and acetylsalicylic acid and similar restriction for 48 h before stool is collected (Rabeneck 2012).

Zhu 2010{10}

Type of care setting

Results demonstrated significant differences in the

analytical performance among different FOBT methods.

Highly sensitive and specific FIT methods may be best suited for colorectal cancer screening programs where testing is performed in a central location. Guaiac-based methods are rapid and easy to perform and are suitable for bedside point-of-care testing albeit a high rate of false positive results should be expected.

Tannous 2009{31}

Sampling strategy used: multiple sample from consecutive stools or one sample

Number of samples for FIT: most kits require one sample, Hemoglobin NS-PLUS two samples over two days, HEMOCCULT ICT 3 samples/3days

A one-day strategy resulted in an intermediate positive rate.

FIT is superior to gFOBT for participation rate (fewer samples, less stool handling).

However, another study in France reported a two day testing (choice based on the fact that CRC bleeding is often intermittent) not to be a barrier to compliance (Faivre 2012)

Rabeneck 2012{15}

Colonoscopy capacity and variation

For all levels of colonoscopy capacity, FIT screening was more effective clinically and in terms of cost compared with gFOBT screening.

FIT should be used at higher hemoglobin cutoff levels when colonoscopy capacity is limited compared with

unlimited  and  is  more  effective  in  terms  of  health  outcomes  and  cost  compared  with  guaiac  FOBT at all colonoscopy capacity levels. Increasing the colonoscopy capacity substantially increases the health benefits of FIT screening

Wilschut 2011{26}

Sensitivity left vs right CRC

Sensitivities for subjects with left-vs right-sided advanced neoplasia were 33% (95% CI, 26 – 41%) and 20% (95% CI: 11 – 31%) at a specificity of 95% (overall sensitivity: 29%) and the areas under the receiver-operating characteristics curve were 0.71 (CI, 0.69 – 0.72) and 0.60 (CI, 0.58 – 0.63), respectively.

In conclusion, the immunochemical FOBT in our study was more sensitive for detecting subjects with left-vs right-sided advanced colorectal neoplasia. Our findings may stimulate further research in the field as well as modelling analyses to estimate the potential effect of site-specific test performance on the programmatic sensitivity and the effectiveness of annual or biennial FOBT based screening programmes, in particular with respect to protection from right-sided CRC.

Haug 2011{32}