An Investigation Into the Cardiovascular Risk and Aetiology of CKDu in Sri Lanka
Condition: CKDu; Arterial Stiffness; Proteinuria; Serum Creatinine; Urinary Biomarkers; DNA Adducts
MeSH terms: Proteinuria
Study type: Observational

Summary: 
      1. We hypothesise that CKDu patients will have increased arterial stiffness and thus
           increased all-cause and cardiovascular mortality. The first objective of this study is
           to recruit a cohort of ~ 50 CKDu patients who attend the CKDu clinic in Anuradhapura,
           and measure their arterial stiffness using the TensioMed® Arteriograph™ (details below).
           We will recruit an age, sex and blood pressure matched control group of healthy Sri
           Lankans (consenting visitors with patients both to clinic and as inpatients), and if
           possible, a second control group, similarly age, sex and blood pressure matched, who
           have CKD of known causes and attend general renal clinic in Anuradhapura.

        2. We hypothesise that detailed renal analysis will give insight into the aetiology of CKDu
           in the North Central Province of Sri Lanka. The second objective of the study is to
           recruit up to 250 CKDu patients and to characterize their disease profile using analysis
           serum and urine renal biomarkers, exosomes, proteomics and DNA adducts.
    

Detailed description: 
      Chronic kidney disease (CKD) is one of the leading causes of hospital admission, clinic
      attendance and mortality in some provinces of Sri Lanka. In central and southern provinces
      increased incidence is attributed to type-2 diabetes and hypertension; however, this is not
      the case in North Central Province (NCP) where CKD of unknown aetiology (CKDu) is the
      commonest diagnosis. A recent World Health Organisation (WHO) investigation concluded that at
      least 8,000 people have CKDu2.

      First recognized in the early nineties, much work has been done to try to characterise the
      disease however results are conflicting. Most suggest male paddy farmers working in rural
      areas of the NCP are worst affected, presenting in their fifth decade with end stage renal
      failure. However, a recent WHO study revealed higher prevalence in females, although more
      severe renal impairment was more common in men.

      Risk factors include inhabiting NCP > five years, inhabiting the 'dry zone', reduced BMI,
      lower socio-economic class, and exposure to agrochemicals. There has been suggestion of a
      genetic link although positive family history is limited to one generation, with no evidence
      of mendelian progression. Epidemiological studies reveal a clustered geographical
      distribution with areas such as Medawachchiya, Padaviya and Girandurukotte most affected.
      High prevalence areas encompass a well-developed irrigation system used for agricultural
      purposes.

      Renal biopsies show tubulointerstitial disease with tubular atrophy, interstitial mononuclear
      cell infiltration, interstitial fibrosis but no immune-complex deposition on
      immunofluorescence. This supports a toxin-mediated process.

      Many aetiologies have been considered including exposure to heavy metals (cadmium, arsenic)
      and their chelation by herbicides, fluro-aluminium complexes, agricultural pesticides,
      mycotoxins, and herbal medicines. Selenium deficiency and genetic susceptibility may be
      predisposing factors. The true aetiology is likely multifactorial.

      The multi-system impact of CKDu has yet to be fully realised. Epidemiological and clinical
      data show that damage to large arteries contributes to the increased cardiovascular risk
      observed in CKD. Atherosclerosis is the most frequent cause of arterial damage but the medial
      calcification seen in CKD also leads to arterial stiffening. This stiffening causes elevation
      in systolic blood pressure, increasing left ventricular workload with the gradual development
      of LVH, and also a fall in diastolic blood pressure impairing coronary blood flow. Arterial
      calcification and stiffness are independent predictors of all-cause and cardiovascular
      mortality in patients with CKD. Arterial stiffness will be compared in CKDu patients, healthy
      Sri Lankan controls and CKD patients both in Sri Lanka and Scotland.

      We will perform a prospective observational study of up to 250 patients with CKDu presenting
      to renal clinics in Teaching Hospital, Anuradhapura. Patient history, basic anthropometric
      measurements, and simple non-invasive tests (e.g. blood pressure and arterial stiffness) will
      be performed. Urine, serum and plasma samples will be collected for quantitative PCR, and
      further analysis for biomarkers of renal injury, exosomes, proteomics and any DNA-adducts.
      Patients will be graded using the WHO CKDu grading system. When a renal biopsy is performed,
      a copy of the light microscopy findings will be obtained. Comparisons of interest will be
      tested via paired t-tests with statistical significance taken at 5%.
    

Intervention name(s): Arterial Stiffness Assessment
Intervention type(s): Device
Intervention description(s): The following will be measured: brachial systolic and diastolic bp, heart rate, mean arterial bp, pulse pressure, brachial augmentation index (difference between the amplitudes of the late (backward) systolic wave (P2) and the early (forward) systolic wave (P1) over the pulse pressure x 100), central augmentation, ejection duration of the left ventricle, return time (time of the pulse wave travelling from aortic root to the bifurcation and back), aortic pulse wave velocity ( velocity of the pulse wave in the aorta), central systolic bp, central pulse pressure and diastolic reflection area (provides information about the quality of diastolic filling in the coronary arteries).
We will perform an arterial age assessment. Patients are given a feedback form with their results to give to their general. Those with increased arterial stiffness will be tested for serum calcium and phosphate levels, and audited to ensure that a statin is commenced if not contraindicated.
Other intervention name(s): TensioMed® Arteriograph™; Pulse wave velocity; Arterial Stiffness Monitor
Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        Patients attending clinics or admitted to hospital during Aug 2014 to Oct 2014 with CKDu
        (Chronic kidney disease of unknown origin).

        Subjects must be aged 18 to 85 with evidence of renal dysfunction and no other obvious
        cause noted (see inclusion/exclusion criteria above).

        Control groups will be sought for the measure of arterial stiffness: Sri Lankan CKD of
        known cause, Sri Lankan healthy volunteers. Our controls will be age, sex and blood
        pressure matched to the cases.
      
Biospecimen description: 
      Urine samples: up to 30ml Blood samples: up to 40ml - 2 x EDTA blood bottles + 2 x serum gel
      Z bottles
    
Keywords: Chronic kidney disease of unknown origin; Chronic kidney disease of unknown aetiology; Sri Lanka; CKDu; Arterial stiffness; Cardiovascular risk; North Central Province