Evaluation of Salt Status in Patients With Cystic Fibrosis

Study Overview
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Brief Summary
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The results of the annual check-up will be collected to evaluate the best urinary marker for fractional sodium excretion and salt status will be correlated to clinical outcome measures.

Detailed Description
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Patients with cystic fibrosis need extra salt as they have increased losses through sweat. Current advices are to follow and supplement if needed, however the way to follow salt depletion is unclear. The best way is to calculate fractional salt excretion. This needs a simultaneous blood and urine sample for electrolytes and creatinin. Urinary surrogate markers have been validated on only 10 patients. At the annual check-up patients with cystic fibrosis receive these measurements. The investigators will collect the measurements and calculate fractional excretion and the possible surrogate markers on urine. Further this will be correlated to nutritional and pulmonary status and patient subgroups at risk will be identified.

Official Title
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Evaluation of Salt Status in Patients With Cystic Fibrosis and the Influence on Nutritional Status and Pulmonary Function. Looking for the Best Surrogate Urinary Markers for Fractional Sodium or Chloride Excretion

Conditions
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Salt; Deficit (or Low), Cystic Fibrosis

Intervention / Treatment
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* Diagnostic Test: fractional sodium excretion
* Other: risk subgroups


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: all cystic fibrosis patients followed at the Gent University Cystic fibrosis centre Providing a paired urine and blood sample at the time of their annual check-up Exclusion Criteria: transplantation
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Diagnostic Test: fractional sodium excretion|fractional sodium excretion will be compared to urinary sodium/creatinin, sodium/potassium ratio's and sodium concentration.|
|Other: risk subgroups|subgroup analysis will be performed to identify the patient groups at risk for sodium depletion|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| fractional sodium excretion (percent) | = (serum creatinin X urinary Sodium)/(plasma sodiumX urinary creatinin) | 1 year | 
| Urinary sodium/urinary creatinin (mmol/mmol) | calculated based on urinary results | 1 year | 
| Fractional Chloride excretion (percent) | = (serum creatinin X urinary Chloride)/(plasma Chloride X urinary creatinin) | 1 year | 
| Fractional Potassium excretion (%) | = (serum creatinin X urinary Potassium)/(plasma PotassiumX urinary creatinin) | 1 year | 
| ratio urinary sodium/urinary potassium | = calculation of ration urinary sodium/potassium | 1 year | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Body mass index | = Weight/Height X Height expressed as SD of the local population based on Flemish growth charts | 1 year | 
| Forced expiratory volume in 1 second | measured with lungfunction testing expressed as % of normal for height | 1 year |