Diagnosis and management of pancreatic exocrine insufficiency (PEI) in primary care: consensus guidance of a Canadian expert panel.

BACKGROUND: Pancreatic exocrine insufficiency (PEI) results in maldigestion due to inadequate activity of pancreatic enzymes in the small bowel. PEI can arise from a variety of medical conditions that reduce enzyme synthesis within the pancreatic parenchyma or from secondary factors that may occur despite optimal parenchymal function, such as pancreatic duct obstruction or impaired or poorly synchronized enzyme release. PURPOSE: To provide practical guidance for primary care physicians managing patients who are at risk of PEI or who present with symptoms of PEI. METHODS: For each of six key clinical questions identified by the authors, PubMed searches were conducted to identify key English-language papers up to April 2017. Forward and backward searches on key articles were conducted using Web of Science. Clinical recommendations proposed by the co-chairs (P.D. and C.T.) were vetted and approved based on the authors? FINDINGS: The most characteristic symptom of PEI is steatorrhea ? voluminous, lipid-rich stools; other common signs and symptoms include unexplained weight loss and deficiencies of fat-soluble vitamins and other micronutrients. Pancreatic enzyme replacement therapy (PERT) can relieve symptoms and long-term sequelae of PEI. Diagnosis of PEI and initiation of PERT are usually the responsibility of gastroenterology specialists. However, primary care physicians (PCPs) are well positioned to identify potential cases of PEI and to participate in the collaborative, long-term management of patients already seen by a specialist. CONCLUSIONS: In this document, a panel of Canadian gastroenterologists has conducted a critical review of the literature on PEI and PERT and has developed practical diagnostic and treatment recommendations for PCPs. These recommendations provide guidance on identifying patients at risk of PEI, the triggers for PEI testing and referral, and best practices for co-managing patients with confirmed PEI.

Simultaneous liver-pancreas transplantation for cystic fibrosis-related liver disease: a multicenter experience.

BACKGROUND: Diabetes is associated with increased morbidity and mortality in patients with cystic fibrosis (CF). While liver transplantation is well established for CF-related liver disease (CFLD), the role of simultaneous liver-pancreas transplantation is less understood. METHODS: We polled 81 pediatric transplantation centers to identify and characterize subjects who had undergone simultaneous liver-pancreas transplantation and obtain opinions about this procedure in CFLD. RESULTS: Fifty (61.7%) polled transplant centers responded and 94% reported that they would consider simultaneous liver-pancreas transplantation for CFLD and diabetes. A total of 8 patients with simultaneous liver-pancreas transplantation were identified with median follow up of 38 months. All patients had pre-existing diabetes. Exocrine and endocrine pancreatic function was initially restored in all patients with later functional loss in one patient. Body mass index Z-score increased between one year pre-transplantation and one year post-transplantation (P=0.029). CONCLUSIONS: Patients with CFLD undergoing initial assessment for liver transplantation may benefit from consideration of simultaneous liver-pancreas transplantation.

Outcomes of patients with cystic fibrosis undergoing lung transplantation with and without cystic fibrosis-associated liver cirrhosis.

People with severe cystic fibrosis (CF) lung disease with co-existent CF-associated liver disease (CFLD) are often excluded from consideration of sole lung transplantation, largely because of the concerns that they will subsequently develop hepatic decompensation. This retrospective cohort study aimed at determining whether patients with severe cirrhosis caused by CFLD have any differences in perioperative and relevant post-transplant outcomes compared to CF patients without CFLD when undergoing sole lung transplantation. Six patients with CFLD were matched with 18 CF patients without CFLD undergoing sole lung transplant at the same institution. There were no differences in total operative time or intra-operative requirements for cardiopulmonary bypass or blood products. Over a period of five yr post-transplant, no differences were observed between the two groups in body mass index, six-min walk, lung function, and survival. None of the CFLD subjects developed variceal bleeding; however, one developed hepatocellular and renal failure at four yr post-transplant and is being assessed for liver-kidney transplant. One additional patient with CFLD required repeat lung transplantation for bronchiolitis obliterans syndrome. This study provides evidence that CF patients with liver cirrhosis caused by CFLD can safely be considered for sole lung transplantation provided there is no evidence of significant hepatocellular dysfunction with decompensated cirrhosis or hepatic synthetic failure.

Cystic fibrosis modifier genes related to Pseudomonas aeruginosa infection.

Cystic fibrosis (CF) is one of the most common life-shortening genetic disorders, and the CF transmembrane conductance regulator (CFTR) is the major causal gene. However, a substantial clinical variability among patients with identical CFTR genotypes suggests the presence of modifier genes. We tested the effect of four genes involved in Pseudomonas aeruginosa infection. Analysis of a primary cohort detected eight candidate polymorphisms that were genotyped in the secondary cohort of 1579 patients; lung function and age at first infection with P. aeruginosa were considered as the phenotypes. Both additive and codominant models were considered, adjusting for confounding variables but not for multiple comparisons. In the secondary cohort, heme oxygenase-1 (HMOX1) rs2071749 had the most significant effect on lung function in the pediatric group (P=0.01; P(corrected)=0.03), and complement factor 3 (C3) rs11569393 and HMOX1 rs2071746 in the adult groups (P=0.03 for both variants; P(corrected)=0.16, 0.09). No polymorphism of complement factor B (CFB) or toll-like receptor 4 (TLR4) had a significant modifying effect on lung function in either group. We have identified two genes that showed nominal association with disease severity among CF patients. However, because of the multiple comparisons made, further studies are required to confirm the interaction between these modifying genes and CFTR.

Understanding the population structure of North American patients with cystic fibrosis.

It is generally presumed that the cystic fibrosis (CF) population is relatively homogeneous, and predominantly of European origin. The complex ethnic make-up observed in the CF patients collected by the North American CF Modifier Gene Consortium has brought this assumption into question, and suggested the potential for population substructure in the three CF study samples collected from North America. It is well appreciated that population substructure can result in spurious genetic associations. To understand the ethnic composition of the North American CF population, and to assess the need for population structure adjustment in genetic association studies with North American CF patients, genome-wide single-nucleotide polymorphisms on 3076 unrelated North American CF patients were used to perform population structure analyses. We compared self-reported ethnicity to genotype-inferred ancestry, and also examined whether geographic distribution and cystic fibrosis transmembrane regulator (CFTR) mutation type could explain the population structure observed. Although largely Caucasian, our analyses identified a considerable number of CF patients with admixed African-Caucasian, Mexican-Caucasian and Indian-Caucasian ancestries. Population substructure was present and comparable across the three studies of the consortium. Neither geographic distribution nor CFTR mutation type explained the population structure. Given the ethnic diversity of the North American CF population, it is essential to carefully detect, estimate and adjust for population substructure to guard against potential spurious findings in CF genetic association studies. Other Mendelian diseases that are presumed to predominantly affect single ethnic groups may also benefit from careful analysis of population structure.

Do common in silico tools predict the clinical consequences of amino-acid substitutions in the CFTR gene?

Computational methods are used to predict the molecular consequences of amino-acid substitutions on the basis of evolutionary conservation or protein structure, but their utility in clinical diagnosis or prediction of disease outcome has not been well validated. We evaluated three popular computer programs, namely, PANTHER, SIFT and PolyPhen, by comparing the predicted clinical outcomes for a group of known CFTR missense mutations against the diagnosis of cystic fibrosis (CF) and clinical manifestations in cohorts of subjects with CF-disease and CFTR-related disorders carrying these mutations. Owing to poor specificity, none of tools reliably distinguished between individual mutations that confer CF disease from mutations found in subjects with a CFTR-related disorder or no disease. Prediction scores for CFTR mutations derived from PANTHER showed a significant overall statistical correlation with the spectrum of disease severity associated with mutations in the CFTR gene. In contrast, PolyPhen- and SIFT-derived scores only showed significant differences between CF-causing and non-CF variants. Current computational methods are not recommended for establishing or excluding a CF diagnosis, notably as a newborn screening strategy or in patients with equivocal test results.

Sweat gland bioelectrics differ in cystic fibrosis: a new concept for potential diagnosis and assessment of CFTR function in cystic fibrosis.

BACKGROUND: For nearly 50 years the diagnosis of cystic fibrosis (CF) has depended on measurements of sweat chloride concentration. While the validity of this test is universally accepted, increasing diagnostic challenges and the search for adequate biomarker assays to support curative-orientated clinical drug trials have created a new demand for accurate, reliable and more practical CF tests. A novel concept is proposed that may provide a more efficient real-time method for assessing CFTR function in vivo. METHODS: Cholinergic and beta-adrenergic agonists were iontophoresed to stimulate sweating. The bioelectric potential from stimulated sweat glands (SPD) was measured in vivo using a standard ECG electrode applied to the skin surface. SPD and sweat chloride concentrations were compared in cohorts predicted to express a range of CFTR function as presented by healthy controls (HC), heterozygotes (Hz), pancreatic sufficient (CFPS) and pancreatic insufficient patients with CF (CFPI). RESULTS: The median SPD was hyperpolarized in patients with CF compared with control subjects (-47.4 mV vs -14.5 mV, p<0.001). In distinguishing between control and CF subjects, SPD (area under receiver operator curve (AUC) = 0.997) was similar to sweat chloride concentration (AUC = 0.986). Sequential cholinergic/beta-adrenergic sweat stimulation dramatically depolarised the SPD in patients with CF (p<0.001) but had no effect in control subjects (p = 0.6) or on the sweat chloride concentration in either group (p>0.5). Furthermore, the positive SPD response was larger in CFPI than in CFPS subjects (p = 0.04). CONCLUSION: These results support the concept that skin surface voltages arising from stimulated sweat glands can be exploited to assess expressed CFTR function in vivo and may prove to be a useful diagnostic tool.

Does the Macroduct collection system reliably define sweat chloride concentration in subjects with intermediate results?

OBJECTIVES: The sweat test remains the current diagnostic gold standard for CF disease. Many CF testing centres have switched from the Gibson and Cooke to the Macroduct. Since the validity and sensitivity of Macroduct has not been tested in patients with intermediate sweat chloride concentrations, we compared both methods simultaneously including subjects expected to have intermediate results. DESIGN AND METHODS: We prospectively evaluated controls, obligate heterozygotes, patients with CF and with an uncertain diagnosis of CF (congenital absence of the vas deferens, pancreatitis and sinopulmonary disease). RESULTS: We assessed 82 subjects (3.7-60.1 years); 14 healthy controls, 7 obligate heterozygotes, 20 CF (15 pancreatic insufficient, 5 pancreatic sufficient), and 41 with unproven diagnosis. Mean test difference was close to 0 (95% CI+/-20 mmol/L) and test values were highly correlated (r=0.93, p < or =0.0001). Discrepancies between the two testing methods occurred in 22% of subjects. CONCLUSION: Sweat chloride measured by Macroduct highly correlates with Gibson and Cooke for concentrations in all ranges, including the intermediate range. This study reveals the limitations of sweat testing for excluding a diagnosis of CF since 38% of subjects had intermediate range results.

Consensus on the use and interpretation of cystic fibrosis mutation analysis in clinical practice.

It is often challenging for the clinician interested in cystic fibrosis (CF) to interpret molecular genetic results, and to integrate them in the diagnostic process. The limitations of genotyping technology, the choice of mutations to be tested, and the clinical context in which the test is administered can all influence how genetic information is interpreted. This paper describes the conclusions of a consensus conference to address the use and interpretation of CF mutation analysis in clinical settings. Although the diagnosis of CF is usually straightforward, care needs to be exercised in the use and interpretation of genetic tests: genotype information is not the final arbiter of a clinical diagnosis of CF or CF transmembrane conductance regulator (CFTR) protein related disorders. The diagnosis of these conditions is primarily based on the clinical presentation, and is supported by evaluation of CFTR function (sweat testing, nasal potential difference) and genetic analysis. None of these features are sufficient on their own to make a diagnosis of CF or CFTR-related disorders. Broad genotype/phenotype associations are useful in epidemiological studies, but CFTR genotype does not accurately predict individual outcome. The use of CFTR genotype for prediction of prognosis in people with CF at the time of their diagnosis is not recommended. The importance of communication between clinicians and medical genetic laboratories is emphasized. The results of testing and their implications should be reported in a manner understandable to the clinicians caring for CF patients.

The prevalence and clinical characteristics of cystic fibrosis in South Asian Canadian immigrants.

BACKGROUND: Cystic fibrosis (CF) is considered to be rare among individuals from the Indian subcontinent. Furthermore, affected individuals are reported to experience a more severe clinical course. AIMS: It was hypothesised that CF is under diagnosed in people of South Asian origin and therefore the prevalence may be higher than previously estimated. METHODS: The prevalence of CF in the South Asian and in the general population living in the same geographic region (Metropolitan Toronto) were compared between 1996 and 2001. Population data were obtained from the Canadian census survey. CF phenotype and genotype data were obtained from the Toronto CF database. RESULTS: Among 381 patients with CF, 15 were of South Asian descent. The age related prevalence of CF among the South Asian and general populations was: 0-14 years, 1:9200 versus 1:6600; 15-24 years, 1:13,200 versus 1:7600; older than 25 years, 1:56,600 versus 1:12,400. Age at diagnosis, duration and severity of symptoms at diagnosis, current nutritional status, and FEV(1) were similar in the two groups. While not significant, FEV1 tended to be lower (48% versus 57% predicted) among adult South Asians, compared to the general CF population. Also, the percentage with pancreatic sufficiency was higher (27% versus 16%) and the frequency of DeltaF508 allele was lower (50% versus 65.1%). CONCLUSIONS: These data suggest that the prevalence and natural history of CF in South Asians is similar to that among individuals of European origin. The relatively lower prevalence among older South Asians may reflect an improving recognition of CF in this ethnic subgroup.

Skeletal phenotype in patients with Shwachman-Diamond syndrome and mutations in SBDS.

Pancreatic exocrine and bone marrow dysfunctions are considered to be universal features of Shwachman-Diamond syndrome (SDS) whereas the associated skeletal dysplasia is variable and not consistently observed. The genetic defect in SDS has recently been identified; causative mutations have been shown in the SBDS gene. The aims of this study were to characterize the nature, frequency, and age-related changes of radiographic skeletal abnormalities in patients with SBDS mutations and to assess genotype-phenotype correlation. Fifteen patients (mean age 9.7 years) with a clinical diagnosis of SDS and documented SBDS gene mutations were included. Review of their skeletal radiographs showed abnormalities in all patients. The skeletal changes were variable, even in patients with identical genotypes. The typical features were (1) delayed appearance of secondary ossification centers, (2) variable widening and irregularity of the metaphyses in early childhood, followed by progressive thickening and irregularity of the growth plates, and (3) generalized osteopenia. There was a tendency towards normalization of the epiphyseal maturation defect and progression of the metaphyseal changes with age. The results suggest that the characteristic skeletal changes are present in all patients with SDS and SBDS mutations, but their severity and localization varies with age. No phenotype-genotype correlation was observed.

Molecular consequences of cystic fibrosis transmembrane regulator (CFTR) gene mutations in the exocrine pancreas.

BACKGROUND AND AIMS: We tested the hypothesis that the actual or predicted consequences of mutations in the cystic fibrosis transmembrane regulator gene correlate with the pancreatic phenotype and with measures of quantitative exocrine pancreatic function. METHODS: We assessed 742 patients with cystic fibrosis for whom genotype and clinical data were available. At diagnosis, 610 were pancreatic insufficient, 110 were pancreatic sufficient, and 22 pancreatic sufficient patients progressed to pancreatic insufficiency after diagnosis. RESULTS: We identified mutations on both alleles in 633 patients (85.3%), on one allele in 95 (12.8%), and on neither allele in 14 (1.9%). Seventy six different mutations were identified. The most common mutation was DeltaF508 (71.3%) followed by G551D (2.9%), G542X (2.3%), 621+1G-->T (1.2%), and W1282X (1.2%). Patients were categorized into five classes according to the predicted functional consequences of each mutation. Over 95% of patients with severe class I, II, and III mutations were pancreatic insufficient or progressed to pancreatic insufficiency. In contrast, patients with mild class IV and V mutations were consistently pancreatic sufficient. In all but four cases each genotype correlated exclusively with the pancreatic phenotype. Quantitative data of acinar and ductular secretion were available in 93 patients. Patients with mutations belonging to classes I, II, and III had greatly reduced acinar and ductular function compared with those with class IV or V mutations. CONCLUSION: The predicted or known functional consequences of specific mutant alleles correlate with the severity of pancreatic disease in cystic fibrosis.

Cystic fibrosis presenting as kwashiorkor in a Sri Lankan infant.

Growth failure is a common presentation of patients with pancreatic insufficient cystic fibrosis. However, full blown kwashiorkor is extremely rare. Cystic fibrosis is also considered to be rare in the South Asian population. This report describes a Sri Lankan infant with cystic fibrosis who presented with clinical features of severe kwashiorkor.

Immune function in patients with Shwachman-Diamond syndrome.

Shwachman-Diamond syndrome (SDS) is an inherited multisystem disorder characterized by exocrine pancreatic dysfunction and varying degrees of cytopenia. In addition, various immunological abnormalities have been noted. To clarify the issue of immunological competence or incompetence in SDS, we prospectively studied immune function in 11 patients with SDS. Seven suffered from recurrent bacterial infections and six from recurrent viral infections. Varying degrees of impairment were readily identified. All patients had neutropenia; total lymphocyte counts, however, were normal in all except one patient. Nine patients had B-cell defects comprising one or more of the following abnormalities: low IgG or IgG subclasses, low percentage of circulating B lymphocytes, decreased in vitro B-lymphocyte proliferation and a lack of specific antibody production. Seven out of nine patients studied had at least one T-cell abnormality comprising a low percentage of total circulating T lymphocytes or CD3+/CD4+ cell subpopulations or decreased in vitro T-lymphocyte proliferation. Five out of six patients studied had decreased percentages of circulating natural killer cells. Moreover, neutrophil chemotaxis was significantly low in all the patients studied. These data point to a major immunodeficiency component in SDS that places patients at heightened risk of infections, even if neutrophil numbers are protective. This finding broadens the definition of the syndrome substantially: it suggests that the SDS marrow defect occurs at the level of an early haematological-lymphocytic stem cell or that a combined marrow and thymic stromal defect accounts for the aberrant function of haematopoietic and lymphopoietic lineages.

Treatment of vitamin K deficiency in cystic fibrosis: Effectiveness of a daily fat-soluble vitamin combination.

OBJECTIVE: Patients with cystic fibrosis (CF) and pancreatic insufficiency (PI) commonly have vitamin K deficiency, and those with CF-associated liver disease (CFLD) have universal vitamin K deficiency. We evaluated the effectiveness of an oral fat-soluble vitamin combination (ADEKs) to treat patients with vitamin K deficiency. STUDY DESIGN: Patients with PI and CF (mean age, 15 years; range, 0.6 to 46 years) including 6 with advanced CFLD were prospectively enrolled in a study of a fat-soluble vitamin combination taken on a daily basis. None had received vitamin K supplementation for at least 4 months before the study. Fat-soluble vitamin combination supplementation was given for a minimum of 4 months; the mean vitamin K intake was 0.18 mg/d (SD = 0.1, range, 0 to 0.3). The primary outcome was change in plasma PIVKA-II (prothrombin in vitamin K absence). RESULTS: Before supplementation 58 (81%) of 72 patients had abnormal PIVKA-II levels (>2.9 ng/mL). After supplementation 29 (40%) had abnormal PIVKA-II levels (P =.001). All 6 patients with advanced CFLD had abnormal PIVKA-II levels (median, range of 20.8, 5.5 to 55 ng/mL) before treatment, which corrected to normal in 50% (4.1, 2.1 to 65 ng/mL). Four patients, 2 with CFLD, had a prolonged prothrombin time (>13.5 seconds) at both time periods. CONCLUSIONS: An oral fat-soluble vitamin combination with a modest amount of vitamin K can, as a daily supplement, improve the PIVKA-II levels in patients with PI and CF.

Shwachman-Diamond syndrome with exocrine pancreatic dysfunction and bone marrow failure maps to the centromeric region of chromosome 7.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by exocrine pancreatic insufficiency and hematologic and skeletal abnormalities. A genomewide scan of families with SDS was terminated at approximately 50% completion, with the identification of chromosome 7 markers that showed linkage with the disease. Finer mapping revealed significant linkage across a broad interval that included the centromere. The maximum two-point LOD score was 8.7, with D7S473, at a recombination fraction of 0. The maximum multipoint LOD score was 10, in the interval between D7S499 and D7S482 (5.4 cM on the female map and 0 cM on the male map), a region delimited by recombinant events detected in affected children. Evidence from all 15 of the multiplex families analyzed provided support for the linkage, consistent with a single locus for SDS. However, the presence of several different mutations is suggested by the heterogeneity of disease-associated haplotypes in the candidate region.

Pancreatic aspects of cystic fibrosis and other inherited causes of pancreatic dysfunction.

Causes of pancreatic dysfunction in childhood can be divided into two general categories: (1) hereditary conditions that directly affect the pancreas and (2) acquired disorders in which loss of pancreatic function is a secondary phenomenon. This article discusses genotypes and phenotypes, clinical features, Shwachman-Diamond syndrome, isolated enzyme deficiencies, and other topics.

Challenges in the dietary treatment of cystic fibrosis related diabetes mellitus.

Cystic fibrosis related diabetes mellitus is an increasingly recognized problem as survival in patients with cystic fibrosis improves. In a 5 year retrospective study of 627 children and adults attending Toronto cystic fibrosis clinics, we identified 57 (9%) patients with cystic fibrosis related diabetes mellitus; four (1.3%) of 301 children (<18 years) and 53 (16%) of 326 adults. The development of this complication of cystic fibrosis is associated with increased mortality, deteriorations in both respiratory and nutritional status, and the development of late microvascular, but not macrovascular, diabetic complications. Unfortunately, systematic review of the literature provides few well designed studies that provide sound evidence for clinical practice. Recommendations are therefore often based on anecdote, rather than physiological or outcomes research. Dietary therapy combines the principles of the dietary management of both cystic fibrosis and diabetes mellitus, but emphasizes the need for a high energy diet (> 100% of recommended daily intake) in patients with cystic fibrosis related diabetes mellitus. The importance of calories from fat is emphasized, with no restriction on total carbohydrate intake. Insulin intake mirrors carbohydrate intake. Routine dietary therapy is straightforward, but challenges occur due to both complications of cystic fibrosis and advancing disease. If a patient with cystic fibrosis related diabetes mellitus is malnourished, overnight enteral tube feeding is often used, with an adjusted insulin regimen. There is a great need for both physiological and outcomes research to provide sound scientific evidence for the dietary treatment of cystic fibrosis related diabetes mellitus.