Diagnostic accuracy of one or two faecal haemoglobin and calprotectin measurements in patients with suspected colorectal cancer.

BACKGROUND: The role of faecal biomarkers in patients at 'high risk' of colorectal cancer (CRC) is not yet defined. Pre-analytical factors, such as heterogeneity of biomarker distribution within faeces, may influence their optimisation in clinical practice. We undertook to determine whether repeat or combined biomarker testing improves diagnostic accuracy for CRC or clinically significant disease. METHODS: Patients referred with suspected CRC provided two separate faecal samples each for faecal immunochemical testing (FIT) and faecal calprotectin (FC) prior to investigation. Diagnostic accuracy of FIT and FC were evaluated based on final diagnoses. RESULTS: Five hundred fifteen patients completed a full colorectal evaluation. The optimal cut-off for CRC using a single FIT was ≥12 µgHb/g faeces (84.6% sensitivity, 88.5% specificity). For two FIT, the cut-off was ≥43 µgHb/g faeces if either and ≥2 µgHb/g faeces if both were positive. There was no advantage in their diagnostic accuracy compared with a single FIT. FC had a lower diagnostic accuracy for CRC than FIT, which was not improved by repeat FC. No benefit was identified with FIT-FC combined. For CRC, significant adenomatous polyps and organic enteric disease combined, FIT and FC performed similarly to each other but were poorer predictors (AUC 0.677 and 0.660). There was no uplift in diagnostic accuracy when the tests were repeated or combined. CONCLUSION: This study supports using a single FIT at a cut-off close to that recommended by NICE DG30 to improve diagnostic accuracy for 'two-week wait' patients referred with suspected CRC.

The Fast Track FIT study: diagnostic accuracy of faecal immunochemical test for haemoglobin in patients with suspected colorectal cancer.

BACKGROUND: The faecal immunochemical test (FIT) is now available to support clinicians in the assessment of patients at low risk of colorectal cancer (CRC) and within the bowel cancer screening programme. AIM: To determine the diagnostic accuracy of FIT for CRC and clinically significant disease in patients referred as they were judged by their GP to fulfil National Institute for Health and Care Excellence guideline 12 (NG12) criteria for suspected CRC. DESIGN AND SETTING: Patients referred from primary care with suspected CRC, meeting NG12 criteria, to 12 secondary care providers in Yorkshire and Humber were asked to complete a FIT before investigation. METHOD: The diagnostic accuracy of FIT based on final diagnosis was evaluated using receiver operating characteristics analysis. This permitted a statistically optimal cut-off value for FIT to be determined based on the maximisation of sensitivity and specificity. Clinicians and patients were blinded to the FIT results. RESULTS: In total, 5040 patients were fully evaluated and CRC was detected in 151 (3.0%). An optimal cut-off value of 19 µg Hb/g faeces for CRC was determined, giving a sensitivity of 85.4% (95% confidence interval [CI] = 78.8% to 90.6%) and specificity of 85.2% (95% CI = 84.1% to 86.2%). The negative predictive value at this cut-off value was 99.5% (95% CI = 99.2% to 99.7%) and the positive predictive value 15.1% (95% CI = 12.8% to 17.7%). Sensitivity and specificity of FIT for CRC and significant premalignant polyps at this cut-off value were 62.9% (95% CI = 57.5% to 68.0%) and 86.4% (95% CI = 85.4% to 87.4%), respectively; and when including all organic enteric disease were 35.7% (95% CI = 32.9% to 38.5%) and 88.6% (95% CI = 87.5% to 89.6%), respectively. CONCLUSION: FIT used in patients fulfilling NG12 criteria should allow for a more personalised CRC risk assessment. FIT should permit effective, patient-centred decision-making to inform the need for, type, and timing of further investigation.

Audit of the impact of the York faecal calprotectin care pathway on colonoscopy activity.

BACKGROUND: The York faecal calprotectin care pathway (YFCCP) was developed to optimise effective primary care differentiation between irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We undertook an audit of colonoscopy activity at York Teaching Hospitals after the introduction of the YFCCP, to assess its impact. METHODS: Faecal calprotectin (FC) results were reconciled with colonoscopy activity in patients 18-60 years after the implementation of the YFCCP. This permitted individual patient tracking of their FC values, the timing of those requests by primary care, the date of subsequent referral and investigation and the end clinical diagnoses. RESULTS: Primary care uptake of FC increased fourfold with the introduction of the YFCCP. Following implementation, FC-related referrals for colonoscopy fell from 24% to 13%. The number of patients needed to colonoscope to diagnose organic colonic disease (IBD, significant adenomatous polyps or colorectal cancer) fell from 6.8 to 3.8 when the YFCCP was applied. This represents a cost saving of £41 015 per thousand patients tested in primary care. We estimate that outpatient time to diagnosis fell from a median of 41 to 29 days. CONCLUSION: This audit of FC activity and colonoscopy outcomes provides substantial supportive evidence for the effectiveness of the YFCCP. Popular in primary care, it has led to a reduction in referrals. The diagnostic accuracy determined in this audit is in line with earlier evaluations. Accepting the weaknesses of audit we conclude that this evaluation likely underestimates the benefits of the YFCCP in terms of resource use saving and time to diagnosis.

A short report: reflective testing in the diagnosis of hereditary haemochromatosis: results of a short retrospective study.

BACKGROUND: Reflective addition of iron studies to elevated ferritin results can be a useful first step towards making a diagnosis of haemochromatosis; however, the criteria for doing so are poorly defined and the efficiency of different stages of this process are not well documented. We studied the efficiency of current practice at York Teaching Hospitals NHS Foundation Trust with the aim to identify areas for improvement. METHODS: Data were gathered from the laboratory database on the number of iron studies and subsequent interpretive comments reflectively added by laboratory staff during an eight-month period. Reflective addition of iron was based on individual practice of the reporter. Standardised interpretive comments were added to suggest HFE genotyping when both the ferritin and transferrin saturation were raised. The number of patients successfully followed up and found to have pathological HFE gene mutations was used to evaluate efficiency. RESULTS: A total of 2651 raised ferritin results were reported during the evaluation period, which resulted in the reflective addition of 381 iron studies and 43 interpretive comments by the duty biochemists. This led to 33 requests for HFE genotyping and the identification of 13 individuals with pathological mutations. The number of iron studies reflectively added to diagnose one patient (NND) was found to be 29.3. CONCLUSIONS: Reflective addition of iron studies and interpretive comments can assist in the early detection of patients with hereditary haemochromatosis. Better guidance for laboratory staff undertaking reflective testing and for general practitioners facilitating patient follow-up may increase the efficiency of this diagnostic process.

Evaluation of sample stability for a quantitative faecal immunochemical test and comparison of two sample collection approaches.

Background Faecal immunochemical testing is increasingly being used to triage symptomatic patients for suspected colorectal cancer. However, there are limited data on the effect of preanalytical factors on faecal haemoglobin when measured by faecal immunochemical testing. The aim of this work was to evaluate the stability of faecal haemoglobin in faeces and to compare two methods of faecal haemoglobin sampling for faecal immunochemical testing. Methods Six patients provided faeces for faecal haemoglobin measurement which were transferred into specialized collection devices at baseline and at 1, 2, 3 and 7 days after storage at either room temperature or 4°C. A total of 137 patients returned both faeces transferred into the specialized collection device and faeces in a standard collection pot. A quantitative immunoturbidometric method was used to measure faecal haemoglobin and results were compared categorically. Discrepant results were assessed against diagnosis. Results Faecal haemoglobin concentration declined rapidly within a day of storage at room temperature but results remained ≥10 µg Hb/g faeces in 5/6 patients after two days. A faecal haemoglobin result ≥10 µg Hb/g faeces was obtained in 4/6 patients after storage for seven days at 4°C. Results obtained when patients used specialized collection devices were significantly different from results obtained when faeces was transferred into the specialized collection device in the laboratory. Conclusion There is considerable heterogeneity in the sample stability of faecal haemoglobin; therefore, samples should be transferred rapidly into specialized collection devices to prevent false-negative results. Use of collection devices by patients can lead to false-positive results compared with their use in a laboratory.

Evaluation of the clinical and cost-effectiveness of the York Faecal Calprotectin Care Pathway.

OBJECTIVE: To evaluate the sensitivity and specificity of the York Faecal Calprotectin Care Pathway (YFCCP) and undertake a health economics analysis. The YFCCP has been introduced in support of the National Institute for Health and Care Excellence (NICE) guidance DG11. It is designed to improve the sensitivity and specificity of faecal calprotectin (FC) in discriminating the irritable bowel syndrome from inflammatory bowel disease in primary care. DESIGN: To prospectively evaluate the clinical outcomes at 6 months of the first 1005 patients entering the YFCCP. To develop a cost-consequence model using two comparators: one based on clinical assessment and the C reactive protein/erythrocyte sedimentation rate without using FC, and the second using single testing of the standard FC cut-off. SETTING: North Yorkshire primary care practices. PATIENTS: Primary care patients fulfilling NICE DG11. INTERVENTIONS: The YFCCP. MAIN OUTCOME MEASURES: Clinical outcome measures from secondary care records. RESULTS: The sensitivity and specificity of the YFCCP are 0.94 (0.85 to 0.98) and 0.92 (0.90 to 0.94), giving a negative and positive predictive value of 0.99 (0.98 to 1.0) and 0.51 (0.43 to 0.59), respectively. CONCLUSIONS: The YFCCP overcomes the challenges experienced with FC use in primary care, its efficacy matching initial NICE projections. It is readily incorporated into clinical practice. It should represent the framework on which to increase NICE DG11 implementation nationally.

The suppression of galactose metabolism in Trypanosoma cruzi epimastigotes causes changes in cell surface molecular architecture and cell morphology.

The cell surface of the epimastigote form of Trypanosoma cruzi is covered by glycoconjugates rich in galactose. The parasite cannot take up galactose through its hexose transporter, suggesting that the epimerisation of UDP-glucose to UDP-galactose may be the parasite's only route to this sugar. The T. cruzi UDP-glucose 4'-epimerase is encoded by the TcGALE gene. We were unable to make a CL-Brener strain T. cruzi epimastigote TcGALE-/- null mutant, suggesting that the gene is essential. Two TcGALE+/- single-allele knockout clones displayed aberrant morphology and haploid deficiency with respect to galactose metabolism. The morphological phenotypes included shortened flagella, increased incidence of spheromastigotes, agglutination and a novel walnut-like appearance. The reduced supply of UDP-galactose was manifest in the two clones as a six- or nine-fold reduction in the expression of galactopyranose-containing cell surface mucins and negligible or two-fold reduction in the expression of galactofuranose-containing glycoinositolphospholipids. The major loss of mucins as opposed to glycoinositolphospholipids may indicate that the latter are more important for basic parasite survival in culture. The apparent haploid deficiency suggests that epimerase levels are close to limiting, at least in the epimastigote form, and might be exploited as a potential drug target.

Evaluation of a faecal calprotectin care pathway for use in primary care.

BACKGROUND: National Institute for Health and Care Excellence have recommended faecal calprotectin (FC) testing as an option in adults with lower gastrointestinal symptoms for whom specialist investigations are being considered, if cancer is not suspected and it is used to support a diagnosis of inflammatory bowel disease (IBD) or irritable bowel syndrome. York Hospital and Vale of York Clinical Commissioning Group have developed an evidence-based care pathway to support this recommendation for use in primary care. It incorporates a higher FC cut-off value, a 'traffic light' system for risk and a clinical management pathway. OBJECTIVES: To evaluate this care pathway. METHODS: The care pathway was introduced into five primary care practices for a period of six months and the clinical outcomes of patients were evaluated. Negative and positive predictive values (NPV and PPV) were calculated. GP feedback of the care pathway was obtained by means of a web-based survey. Comparator gastroenterology activity in a neighbouring trust was obtained. RESULTS: The care pathway for FC in primary care had a 97% NPV and a 40% PPV. This was better than GP clinical judgement alone and doubled the PPV compared with the standard FC cut-off (250 mcg/g and were diagnosed by 'straight to test' colonoscopy within three weeks. The care pathway was considered helpful by GPs and delivered a higher diagnostic yield after secondary care referral (21%) than the conventional comparator pathway (5%). CONCLUSIONS: A care pathway for the use of FC that incorporates a higher cut-off value, a 'traffic light' system for risk and supports clinical decision making can be achieved safely and effectively. It maintains the balance between a high NPV and an acceptable PPV. A modified care pathway for the use of FC in primary care is proposed.

Faecal calprotectin in patients with suspected colorectal cancer: a diagnostic accuracy study.

BACKGROUND: NICE guidance exists for the use of faecal calprotectin (FC) when irritable bowel syndrome or inflammatory bowel disease are suspected. Often, however, colorectal cancer is considered within the differential. Should FC have a high diagnostic accuracy for colorectal cancer, it may be applicable as a primary care screening test for all patients with lower gastrointestinal symptoms. AIM: To determine the negative and positive predictive value (NPV/PPV) of FC in patients referred from primary care with suspected colorectal cancer. DESIGN AND SETTING: A diagnostic accuracy study conducted at a single secondary care site METHOD: Consenting patients referred with suspected colorectal cancer within the '2-week wait' pathway provided a stool sample for FC prior to investigation. FC levels were reconciled with end diagnoses: cancer, adenomatous polyps ≥10 mm, and all enteric organic disease. RESULTS: A total of 654 patients completed the evaluation; median age 69 years, female 56%. The NPV for colorectal cancer was 98.6% and 97.2% when including polyps ≥10 mm. The PPV for all organic enteric disease was 32.7%. The diagnostic yield for cancer based on clinical suspicion was 6.3%. By altering the FC cut-off to fix the NPV at 97.0%, the PPV for cancer increased from 8.7% to 13.3%. CONCLUSION: FC has a high NPV for colorectal cancer and significant polyps in patients with suspected cancer. In total, 27.8% of patients had a normal FC and could safely have been spared a '2-week wait' referral. The addition of FC testing into the current symptom-based assessment has the potential to increase colorectal cancer detection rate yet be clinically and cost effective.

Protein O-GlcNAcylation is required for fibroblast growth factor signaling in Drosophila.

Glycosylation is essential for growth factor signaling through N-glycosylation of ligands and receptors and the biosynthesis of proteoglycans as co-receptors. Here, we show that protein O-GlcNAcylation is crucial for fibroblast growth factor (FGF) signaling in Drosophila. We found that nesthocker (nst) encodes a phosphoacetylglucosamine mutase and that nst mutant embryos exhibited low amounts of intracellular uridine 5'-diphosphate-N-acetylglucosamine (UDP-GlcNAc), which disrupted protein O-GlcNAcylation. Nst was required for mitogen-activated protein kinase (MAPK) signaling downstream of FGF but not MAPK signaling activated by epidermal growth factor. nst was dispensable for the function of the FGF ligands and the FGF receptor's extracellular domain but was essential in the signal-receiving cells downstream of the FGF receptor. We identified the adaptor protein Downstream of FGF receptor (Dof), which interacts with the FGF receptor, as the relevant target for O-GlcNAcylation in the FGF pathway, suggesting that protein O-GlcNAcylation of the activated receptor complex is essential for FGF signal transduction.

The synthesis of UDP-N-acetylglucosamine is essential for bloodstream form trypanosoma brucei in vitro and in vivo and UDP-N-acetylglucosamine starvation reveals a hierarchy in parasite protein glycosylation.

A gene encoding Trypanosoma brucei UDP-N-acetylglucosamine pyrophosphorylase was identified, and the recombinant protein was shown to have enzymatic activity. The parasite enzyme is unusual in having a strict substrate specificity for N-acetylglucosamine 1-phosphate and in being located inside a peroxisome-like microbody, the glycosome. A bloodstream form T. brucei conditional null mutant was constructed and shown to be unable to sustain growth in vitro or in vivo under nonpermissive conditions, demonstrating that there are no alternative metabolic or nutritional routes to UDP-N-acetylglucosamine and providing a genetic validation for the enzyme as a potential drug target. The conditional null mutant was also used to investigate the effects of N-acetylglucosamine starvation in the parasite. After 48 h under nonpermissive conditions, about 24 h before cell lysis, the status of parasite glycoprotein glycosylation was assessed. Under these conditions, UDP-N-acetylglucosamine levels were less than 5% of wild type. Lectin blotting and fluorescence microscopy with tomato lectin revealed that poly-N-acetyllactosamine structures were greatly reduced in the parasite. The principal parasite surface coat component, the variant surface glycoprotein, was also analyzed. Endoglycosidase digestions and mass spectrometry showed that, under UDP-N-acetylglucosamine starvation, the variant surface glycoprotein was specifically underglycosylated at its C-terminal Asn-428 N-glycosylation site. The significance of this finding, with respect to the hierarchy of site-specific N-glycosylation in T. brucei, is discussed.

Sugar nucleotide pools of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major.

The cell surface glycoconjugates of trypanosomatid parasites are intimately involved in parasite survival, infectivity, and virulence in their insect vectors and mammalian hosts. Although there is a considerable body of work describing their structure, biosynthesis, and function, little is known about the sugar nucleotide pools that fuel their biosynthesis. In order to identify and quantify parasite sugar nucleotides, we developed an analytical method based on liquid chromatography-electrospray ionization-tandem mass spectrometry using multiple reaction monitoring. This method was applied to the bloodstream and procyclic forms of Trypanosoma brucei, the epimastigote form of T. cruzi, and the promastigote form of Leishmania major. Five sugar nucleotides, GDP-alpha-d-mannose, UDP-alpha-d-N-acetylglucosamine, UDP-alpha-d-glucose, UDP-alpha-galactopyranose, and GDP-beta-l-fucose, were common to all three species; one, UDP-alpha-d-galactofuranose, was common to T. cruzi and L. major; three, UDP-beta-l-rhamnopyranose, UDP-alpha-d-xylose, and UDP-alpha-d-glucuronic acid, were found only in T. cruzi; and one, GDP-alpha-d-arabinopyranose, was found only in L. major. The estimated demands for each monosaccharide suggest that sugar nucleotide pools are turned over at very different rates, from seconds to hours. The sugar nucleotide survey, together with a review of the literature, was used to define the routes to these important metabolites and to annotate relevant genes in the trypanosomatid genomes.

The de novo synthesis of GDP-fucose is essential for flagellar adhesion and cell growth in Trypanosoma brucei.

The protozoan parasite Trypanosoma brucei causes human African sleeping sickness in sub-Saharan Africa. The parasite makes several essential glycoproteins, which has led to the investigation of the sugar nucleotides and glycosyltransferases required to synthesize these structures. Fucose is a common sugar in glycoconjugates from many organisms; however, the sugar nucleotide donor GDP-fucose was only recently detected in T. brucei, and the importance of fucose metabolism in this organism is not known. In this paper, we identified the genes encoding functional GDP-fucose biosynthesis enzymes in T. brucei and created conditional null mutants of TbGMD, the gene encoding the first enzyme in the pathway from GDP-mannose to GDP-fucose, in both bloodstream form and procyclic form parasites. Under nonpermissive conditions, both life cycle forms of the parasite became depleted in GDP-fucose and suffered growth arrest, demonstrating that fucose metabolism is essential to both life cycle stages. In procyclic form parasites, flagellar detachment from the cell body was also observed under nonpermissive conditions, suggesting that fucose plays a significant role in flagellar adhesion. Fluorescence microscopy of epitope-tagged TbGMD revealed that this enzyme is localized in glycosomes, despite the absence of PTS-1 or PTS-2 target sequences.

Galactose starvation in a bloodstream form Trypanosoma brucei UDP-glucose 4'-epimerase conditional null mutant.

Galactose metabolism is essential for the survival of Trypanosoma brucei, the etiological agent of African sleeping sickness. T. brucei hexose transporters are unable to transport galactose, which is instead obtained through the epimerization of UDP-glucose to UDP-galactose catalyzed by UDP-glucose 4'-epimerase (galE). Here, we have characterized the phenotype of a bloodstream form T. brucei galE conditional null mutant under nonpermissive conditions that induced galactose starvation. Cellular levels of UDP-galactose dropped rapidly upon induction of galactose starvation, reaching undetectable levels after 72 h. Analysis of extracted glycoproteins by ricin and tomato lectin blotting showed that terminal beta-d-galactose was virtually eliminated and poly-N-acetyllactosamine structures were substantially reduced. Mass spectrometric analysis of variant surface glycoprotein confirmed complete loss of galactose from the glycosylphosphatidylinositol anchor. After 96 h, cell division ceased, and electron microscopy revealed that the cells had adopted a morphologically distinct stumpy-like form, concurrent with the appearance of aberrant vesicles close to the flagellar pocket. These data demonstrate that the UDP-glucose 4'-epimerase is essential for the production of UDP-galactose required for galactosylation of glycoproteins and that galactosylation of one or more glycoproteins, most likely in the lysosomal/endosomal system, is essential for the survival of bloodstream form T. brucei.