ABSTRACT
Background: Hyperphosphataemia (serum phosphate>1.7mmol/L) in end stage renal disease is independently linked to higher rates of morbidity and mortality and effects 30% of haemodialysis (HD) patients in the UK[1,2]. Current dietary practices focus on reducing the intake of naturally sourced phosphate to 800-1000mg/day and highly nutritious foods are often limited. Phosphate-containing additives (PCA), of which there are 14 listed by the European Commission, may be contributing an additional 1000mg phosphate per day [3]; it is therefore important to have knowledge of this source of phosphate in the diet. The aim of the service evaluation was to assess the relationship between dialysis parameters, medication, dietary intake of phosphate and PCA on the management of hyperphosphataemia. Method: 24 established (>90days) adult HD patients were recruited from Kent and Canterbury Renal Unit. Intake of phosphate binders and dietary information were collected using a 3-day diet diary (not weighed) and a questionnaire to clarify intake of high phosphate foods and phosphate binders. Phosphate-containing additives were considered using the weight of processed foods containing at least one such additive, stated on packaging or online nutritional databases. In addition, efficiency of HD (Kt/V) and residual renal function using glomerular filtration rate (GFR) and urine output, were considered. DietPlan6 and SPSS were used for data analysis. Statistical tests assessed data distribution, Pearson correlation and any differences in variables between patients with and without hyperphosphataemia (T-test). Ethical approval was granted by the University of Surrey, NHS ethics not required as it was a service evaluation. Results: The average serum phosphate was 1.73±0.52mmol/L, 38% of patients had hyperphosphataemia (>1.7mmol/L) and 79% of patients were prescribed a phosphate binder. 19/24 patients returned the 3-day diet diary and questionnaire. Mean phosphate intake was 884±278mg/day with approximately 85% of patients consuming less phosphate, energy and protein per kilogram per day than recommended (Table 1). Processed foods containing PCA were positively correlated to serum phosphate levels (r2=0.234, p=0.036), however, correlation no longer existed once outliers were excluded (r2=0.114, p=0.184). Serum potassium also correlated with the intake of processed food (r2=0.326, p = 0.017). 47% of patients had inadequate dialysis (Kt/V<1.2) and 71% of patients produced less than 500ml of urine per day. Mean GFR was significantly lower in patients with hyperphosphataemia; 7.25ml/min vs 5.8ml/min (p=0.021). Discussion: The outliers regarding the consumption of phosphate-containing food additives were largely due to high consumption of high phosphate soft drinks (eg cola). Overall intake, including phosphate, maybe underestimated as weighed food diaries were not used, however the fact that both serum phosphate and potassium correlate with intake of processed food has implications for dietary advice and recommendations. Inadequate dialysis may also be an important factor in hyperphosphataemia and needs to be addressed by the multidisciplinary team. Conclusion: Maximising dialysis dose will improve both phosphate and potassium levels and should perhaps be considered before increasing dietary restrictions.Disclosure of phosphate and potassium content on food and drink packaging would help determine more accurately the impact of food additives on biochemistry levels in renal patients.
ABSTRACT
Hepatitis E virus (HEV) is classified within the family Hepeviridae, genus Hepevirus. HEV genotype 3 (Gt3) infections are endemic in pigs in Western Europe and in North and South America and cause zoonotic infections in humans. Several serological assays to detect HEV antibodies in pigs have been developed, at first mainly based on HEV genotype 1 (Gt1) antigens. To develop a sensitive HEV Gt3 ELISA, a recombinant baculovirus expression product of HEV Gt3 open reading frame-2 was produced and coated onto polystyrene ELISA plates. After incubation of porcine sera, bound HEV antibodies were detected with anti-porcine anti-IgG and anti-IgM conjugates. For primary estimation of sensitivity and specificity of the assay, sets of sera were used from pigs experimentally infected with HEV Gt3. For further validation of the assay and to set the cutoff value, a batch of 1100 pig sera was used. All pig sera were tested using the developed HEV Gt3 assay and two other serologic assays based on HEV Gt1 antigens. Since there is no gold standard available for HEV antibody testing, further validation and a definite setting of the cutoff of the developed HEV Gt3 assay were performed using a statistical approach based on Bayes' theorem. The developed and validated HEV antibody assay showed effective detection of HEV-specific antibodies. This assay can contribute to an improved detection of HEV antibodies and enable more reliable estimates of the prevalence of HEV Gt3 in swine in different regions.