Colorectal Cancer Screening Using Immunochemical Fecal Occult Blood Test

Background: Colorectal Cancer in Malaysia

Colorectal cancer (CRC) represents a major and growing public health concern in Malaysia. It is among the most commonly diagnosed cancers in the country, affecting both men and women, and is a leading cause of cancer-related death. The incidence of CRC in Malaysia has been rising steadily over the past several decades, a trend attributed to the adoption of Western dietary patterns, increasing obesity rates, physical inactivity, and the ageing of the population. Among the major ethnic groups in Malaysia, Chinese Malaysians have historically had the highest incidence rates, though rates are increasing across all ethnic groups.

Despite the availability of effective screening tools, participation in colorectal cancer screening in Malaysia remains low. This is partly attributable to limited public awareness of CRC and its preventability, cultural barriers to stool-based testing, insufficient healthcare infrastructure for population-wide screening, and the cost and accessibility challenges associated with colonoscopy. The development and validation of affordable, practical screening tools that can be deployed at the primary care level is therefore essential for improving early detection and reducing CRC mortality in the Malaysian population.

The Immunochemical Fecal Occult Blood Test

Fecal occult blood testing (FOBT) has been a cornerstone of colorectal cancer screening for several decades. The principle underlying FOBT is straightforward: colorectal tumours and large polyps tend to bleed into the bowel lumen, and this blood—though often invisible to the naked eye—can be detected in stool specimens using laboratory assays. However, the conventional guaiac-based FOBT (gFOBT) has significant limitations that have hampered its effectiveness as a screening tool. The guaiac test detects the peroxidase-like activity of haemoglobin through a chemical reaction, but this reaction can be triggered by non-human haemoglobin (from dietary meat), certain vegetables, and medications, leading to false-positive results and the need for dietary restrictions before testing.

The immunochemical FOBT (iFOBT), also known as the fecal immunochemical test (FIT), addresses these limitations by using antibodies specific to human haemoglobin. This immunological approach means that the test is not affected by dietary haemoglobin from animal sources, eliminates the need for pre-test dietary restrictions, can detect lower concentrations of human blood in stool, and is specific to bleeding from the lower gastrointestinal tract (since haemoglobin from the upper GI tract is degraded during passage).

Evidence for FIT in Screening Programmes

The evidence supporting FIT as a population screening tool for CRC has accumulated from both randomised controlled trials and large-scale programmatic evaluations. Screening with the conventional gFOBT has been shown in randomised trials to reduce CRC mortality by approximately one-third, establishing the principle that stool-based screening saves lives. FIT-based screening is expected to provide even greater mortality reduction due to its higher sensitivity, though long-term randomised trial data comparing FIT directly to colonoscopy are still maturing.

Large population-based screening programmes using FIT have been implemented in several countries, including Japan (which pioneered immunochemical screening), Australia, the Netherlands, and parts of the United Kingdom. These programmes have consistently demonstrated that FIT achieves acceptable participation rates—often higher than those achieved with gFOBT, likely due to the simpler collection procedure—while detecting cancers at earlier, more treatable stages. Programmatic data show that the specificity of FIT is routinely above 95%, with sensitivities for CRC ranging from 70% to 80% depending on the specific test product and the haemoglobin concentration cutoff used.

Applicability to the Malaysian Context

The Malaysian healthcare system combines a publicly funded primary care network with private sector providers, creating both opportunities and challenges for screening programme implementation. The public primary care clinics (Klinik Kesihatan) that serve the majority of the population represent a natural platform for FIT distribution, but their current capacity for systematic screening management—including result tracking, follow-up coordination, and quality assurance—would need to be strengthened.

A critical consideration for FIT implementation in Malaysia is the availability of colonoscopy services for diagnostic follow-up. Typically, between 5% and 10% of individuals screened with FIT will have a positive result requiring colonoscopy. In a national screening programme, this would generate thousands of colonoscopy referrals annually, potentially straining the capacity of gastroenterology services. Strategic planning for colonoscopy capacity expansion, including the training of additional endoscopists and the establishment of dedicated screening colonoscopy lists, would be essential prerequisites for FIT programme rollout.

The cultural acceptability of stool-based testing in Malaysia has not been extensively studied but is an important consideration. Anecdotal evidence suggests that some individuals may find stool collection embarrassing or distasteful, though the simplified single-sample collection required by FIT (compared to the multi-sample gFOBT) may mitigate this barrier. Public awareness campaigns that normalise CRC screening and emphasise the life-saving potential of early detection would be an important component of any implementation strategy.

Integration with Malaysia’s National Cancer Control Strategy

Colorectal cancer screening aligns with Malaysia’s broader commitments to non-communicable disease prevention and cancer control. The implementation of population-based CRC screening using FIT would complement existing cancer screening programmes (such as cervical cancer screening with Pap smears and breast cancer screening with mammography) and contribute to the goal of reducing premature mortality from cancer. The relatively low per-test cost of FIT, combined with its suitability for self-collection, makes it one of the most cost-effective cancer screening interventions available.

For population-based screening to achieve its full mortality reduction potential, however, high participation rates and robust quality assurance systems are essential. International experience has demonstrated that organised screening programmes—with systematic invitation, tracking, and follow-up systems—achieve substantially better outcomes than opportunistic screening approaches. Malaysia’s Unique Identification system and electronic health records could facilitate the development of such organised approaches.

Limitations and Considerations

While FIT represents a significant advance over gFOBT, it is not a perfect screening tool. Its sensitivity for advanced adenomas (precancerous polyps) is considerably lower than its sensitivity for CRC, meaning that some individuals with significant precancerous lesions will receive false-negative results. A single round of FIT screening will miss approximately 20–30% of CRCs, underscoring the importance of annual or biennial repeat screening to achieve cumulative detection benefits. Additionally, FIT does not replace the need for colonoscopy in individuals with a family history of CRC or other high-risk factors, for whom direct colonoscopic surveillance is recommended. The evidence base continues to evolve, and ongoing research into combined testing approaches may further improve screening performance in the future.