Epidemiology of CKD

Question 1

Compare and contrast the formulae for calculating GFR

Answer 1

Formulae to define and stage CKD have developed over time
- formulae:
- MDRD - 1st generation, accounted for race, sex and age
- CKD-EPI - a vast improvement
- GFR used to classify stages of CKD, according to KDOQI and now KDIGO
- KDOQI included 40% of the population in stage 2
- Hence, KDIGO accounts for GFR and albuminuria
- it also demonstrates that someone with abnormal levels of albumin in urine, coupled with normal GFR, is actually at high risk of damage
- similarly at higher risk of all cause mortality, CV events, ESKD, AKI and progressive CKD

Question 2

How is CKD defined?

Answer 2

It is either the presence of GFR < 60, OR, markers of perturbed kidney function:
- albuminuria
- urinary sediment abnormalities
- electrolytes
- structural or histological abnormalities

Question 3

Discuss the methods used to measure GFR

Answer 3

• always an estimate i.e. eGFR
• serum creatinine: dependent on size, muscle mass and renal function
  
  • for example, two people with the same size, same creatinine levels but different sex –> female kidney will be performing lower, assuming typical muscle mass per sex
• MDRD or CKD-EPI: both of which are based on serum creatinine
  
  • CKD-EPI more accurate, and has, to some extent, accounted for creatinine differences ^[though not entirely]
• creatinien clearance over 24 hours, which is more accurate but subject to human errors
• radio-isotope scans: DTPA Cr-EDTA, again, more accurate, but is invasive, and is costly

Question 4

Discuss evidence for the performance CKD-EPI formula

Answer 4

• **Reclassified 24.4% to higher eGFR category ^[i.e. better kidney performance]
• 0.6% to lower eGFR category**
• Prevalence of stages 3-5 falls from 8.7% to 6.3%
  
  • Stage 3a. (45-59ml/min). 34.7% reclassified to CKD2 (60-90)
• Those reclassified had lower risks for outcomes:
  
  • 9.9 vs 34.5% (per 1000 person yrs) for all cause mortality
  • 2.7 vs 13% for CVS mortality
  • 0.5 vs 0.8 for ESRF

Note: the substance measured is the same i.e. creatinine, but tools changed to produce different result. Changes CKD epidemiology as a consequence

Question 5

Discuss the pros and cons of the CKD-EPI formula

Answer 5

• helpful as an estimate
• poor in estimating normal function
• useless in ESRF
• used with proteinuria to risk stratify

Question 6

Discuss global statistics relating to CKD

Answer 6

• overall, 34% globally in 1990 (incidence per 100k)
  
  • over-represented in high SDI populations, increasing in low SDI populations
  • note: lack of data from developing nations, age structures skews data reporting
  • race disparity in RRT access, prevalence

Question 7

Discuss predicted trends in ESRD, CKD and how they matched up to actual data

Answer 7

• prevalence of treated ESKD is increasing: 6-5 between 2011 and 2020- but degree of increase less than anticipated
• largest increase over 75 y- more than anticipated ^[why?]
• rate of new cases of treated ESKD is constant
  Note:
• diabetes prevalence in treated ESKD expected to increase- proven correct
• prevalence without diabetes also expected to increase, but by smaller margin
• therefore, diabetes is contributing to increase in treated ESKD

Additional notes: NT and race/locale disparities re: transplants, overall rates

Method of dialysis overwhelmingly satellite in Aus, and rising. Home and PD options limited.

Question 8

Discuss the epidemiology of proteinuria, diabetes, haematuria and renal impairment

Answer 8

Ausdiab study
- diabetes prevalence in treated ESKD expected to increase
- prevalence without diabetes also expected to increase, but by smaller margin
- therefore, diabetes is contributing to increase in treated ESKD

Proteinuria
- men and women **over 65
- fairly mild overall

Haematuria
- women (periods)
- women over 65 y
- men over 65 y (equal?)

Renal impairment
- 1% in class 4-5
- mostly class 3
- over 65s biggest proportion: risk of blood pressure and cardiovascular issues

Question 9

Discuss the epidemiology of PKD

Answer 9

• Affects 1 in 400 to 1000 people
  
  • Occurs worldwide and in all races
  • Increase in renal size, cyst formation, haemorrhage, infection
  • Hypertension in 75% of patients before renal failure
  • Extra-renal cysts (liver and pancreas most common)
  • Increased risk of renal stones – uric acid or calcium oxalate
  • 77% alive with preserved renal function age 50
  • 52% age 70.
  • Make up 7% of end stage population
  • Progression related to genotype (PKD1 higher risk than PKD2)

Question 10

Discuss the epidemiology of glomerulonephritis

Answer 10

• 24% of end stage population
  
  • IgA GN most common but variable around the world
  • Variable presentation at different ages
    
    • 40—50% macroscopic haematuria
    • 40% with asymptomatic urinary abnormalities
• Large differences between races (prevalence in se Asia, due to Hepatitis B prevalence, and genetics)
  
  • Prevalence of mild IgA from renal biopsy study 1.6% in Japan
    Outcome highly variable.
• age-spread across various glomerulonephritis also large
• Survival differs

Question 11

Discuss findings from the global burden of disease study

Answer 11

• 700k cases in 2019, 10k deaths, 300k DALYs
  
  • rate irrespective of sex
  • prev decrease, mortality larger decrease ^[doubt due to change in tools used to assess, esp. mortality]
  • DALY: does not account for YLD
  • Similarly in comparing SDI and DALYs, data collection issues cast doubt on figures
  • Age structures and data collection affects interpretation of data
    
    • e.g. low SDI, drop in incidence over time: population growth
    • proven by age-standardised rates
    • dec and increase in figures: improved data collection and healthcare capacity