Faecal haemoglobin concentrations are associated with all-cause mortality and cause of death in colorectal cancer screening

Engineering coupled consortia-based biosensors for diagnostic

Synthetic multicellular systems have great potential for performing complex tasks, including multi-signal detection and computation through cell-to-cell communication. However, engineering these systems is challenging, requiring precise control over the cell concentrations of distinct members and coordination of their activity. Here, we develop a bacterial consortia-based biosensor for Heme and Lactate, wherein members are coupled through a global shared quorum-sensing signal that simultaneously controls the activity of the diverse biosensing strains. The multicellular system incorporates a gene circuit that computes the minimum between each biosensor's activity and the shared signal. We evaluate three consortia configurations: one where the shared signal is externally supplied, another directly produced via an inducible gene circuit, and a third generated through an incoherent feedforward loop (IFFL) gene circuit. Among these configurations, the IFFL system, which maintains the shared signal at low and stable levels over an extended period, demonstrates improved performance and robustness against perturbations in cell populations. Finally, we examine these coupled consortia to monitor Lactate and Heme in humanized fecal samples for diagnostics.

Systematic review: Mortality associated with raised faecal immunochemical test and positive faecal occult blood results

BACKGROUND

Faecal haemoglobin (f-Hb) testing is used in colorectal cancer (CRC) screening and increasingly to guide the investigation in patients with symptoms suggestive of CRC. Studies have demonstrated increased mortality with raised f-Hb.

AIMS

To assess the association of raised f-Hb with all-cause, non-CRC (any cause excluding CRC) and cause-specific mortality.

METHODS

We searched Medline and Embase on 9 February 2024 to identify papers reporting mortality after faecal immunochemical (FIT) or guaiac faecal occult blood tests (gFOBT). The primary outcome was all-cause mortality following a positive compared to a negative test.

RESULTS

The search identified 3155 papers. Ten met the inclusion criteria: three reported gFOBT and seven reported FIT results, as screening tests. These reported a total of 14,687,625 f-Hb results. Elevated f-Hb was associated with an increased risk of all-cause, non-CRC and cause-specific mortality including death from cardiovascular, digestive and respiratory diseases. Crude risk ratios for all-cause mortality with a positive versus negative test were derived from six papers (three reporting gFOBT, three FIT). An increased risk was demonstrated in five, with RRs ranging from 1.11 (95% CI: 1.06-1.16) to 2.95 (95% CI: 2.85-3.05). For non-CRC mortality risk, RRs ranged from 1.09 (95% CI: 1.04-1.15) to 2.79 (95% CI: 2.70-2.89). We did not perform meta-analysis due to a limited number of papers reporting suitable results for each type of f-Hb test.

CONCLUSIONS

All-cause, non-CRC and cause-specific mortality appear higher in those with raised f-Hb. Population-based studies are warranted to elicit whether this association occurs in symptomatic patients.

The structure of a haemoglobin-nanobody complex reveals human β-subunit-specific interactions

Haemoglobin (Hb) is a vital oxygen carrier in vertebrates. Low blood Hb levels may indicate anaemia or genetic disorders, while its presence in the lower digestive system suggests colon cancer. Detecting and quantifying human Hb is essential for medical diagnostics. A nanobody-based sandwich-ELISA test was recently developed utilising llama-derived nanobodies NbE11 and NbB9. These nanobodies specifically bind to human Hb without cross-reacting with Hb from other vertebrates. Here, we determine the crystal structure of NbE11 in complex with human Hb. NbE11 binds Hb with high affinity, predominantly binding the β-Hb subunit. Structural differences between human Hb and other vertebrates at the NbE11 binding interface likely explain the assay's lack of cross-reactivity, providing insights for developing Hb binding diagnostics.

Factors associated with negative colonoscopy in participants with a positive faecal immunochemical test from the Danish Colorectal Cancer Screening Program - a population-based study

AIM

In the Danish Colorectal Cancer Screening Program (DCCSP), 37% of participants undergoing colonoscopy have a negative result with no obvious findings that can be attributed to a positive faecal immunochemical test (FIT). The aim of this work was to identify predictors for a negative colonoscopy in DCCSP participants with a positive FIT.

METHOD

We included 73 655 FIT-positive DCCSP participants using the Danish Colorectal Cancer Screening Database and linked their screening results with data from several other national health registers. We stratified participants by all predictors, and compared them using multivariate logistic regression analysis. Results are reported as odds ratios (ORs).

RESULTS

We found that having a condition linked to gastrointestinal bleeding, for example fissures, haemorrhoids and inflammatory bowel disease, was strongly associated with the probability of having a negative colonoscopy [OR 2.77 (95% CI 2.59, 2.96)]. FIT concentration was inversely related to the probability of a negative colonoscopy, the OR decreased steadily from 0.79 (95% CI 0.75, 0.83) in the 40-59 μg/g group, to 0.44 (95% CI 0.42, 0.46) in the ≥200 μg/g group. Women had a 1.64 (95% CI 1.59, 1.70) times higher probability of a negative colonoscopy than men.

CONCLUSION

Our findings indicate that baseline conditions linked to gastrointestinal bleeding are an associating factor with having a negative colonoscopy. The same is true for low FIT concentration and female sex. Further studies with similar findings could suggest that an incorporation of these factors into a personalized screening approach by differentiating between diagnostic modalities could improve the process for the participant while alleviating the health care system.

Faecal haemoglobin: Measurement, applications, and future potential

Faecal hemoglobin concentrations (f-Hb) can be quantitated using faecal immunochemical test for haemoglobin (FIT) analytical systems. FIT are of proven value and widely used in colorectal cancer (CRC) screening. Several factors affect f-Hb including sex, age, deprivation, geographical region, and FIT system. Thus, FIT data may not be transferable. Women are disadvantaged in programmes using a single f-Hb threshold for all participants, but risk scoring or sex stratified thresholds could be used to minimise this problem. In addition, low but detectable f-Hb, below the threshold, implies future risk of CRC. In several countries, where colonoscopy resources are constrained, FIT are now accepted as of added value in assessment of patients presenting in primary or secondary care with symptoms, although some serious colorectal disease is missed. Elevated f-Hb in the absence of any discernible colorectal lesions is common and has been found in several diseases with a systemic inflammatory component, including circulatory, respiratory, digestive, neuropsychological, blood and endocrine diseases, and others. There is growing evidence for the value of f-Hb in post-polypectomy surveillance, potentially saving costs and colonoscopy. There may be a role for FIT systems which have lower limits of detection than currently available methods. The faecal material remaining in FIT specimen collection devices could be used for further studies, including assessment of the microbiome. The estimation of f-Hb is now a mature investigative tool but further research will undoubtedly expand applications of value.