Prevalence, socio-demographic characteristics, and comorbid health conditions in pre-dialysis chronic kidney disease: results from the Manitoba chronic kidney disease cohort

Chronic kidney disease (CKD) is a common disorder requiring a public health surveillance strategy to identify those at risk of progression and treat them with disease modifying therapies [1]. Epidemiological studies report that CKD is highly prevalent in the general population and that it has increased steadily over several decades [2‐4]. Not surprisingly, parallel to these increases in CKD, increases in the prevalence of kidney failure, or End Stage Kidney Disease (ESKD), have also been reported [5, 6]. ESKD is associated with comorbid health conditions, poor quality of life, and high health care costs [7].

It is critical to develop innovative methods to estimate CKD prevalence and identify affected individuals requiring treatment. Kidney failure affects more Manitobans per capita than most other provinces in Canada, with a prevalence rate of 1530 per million population compared to the Canadian rate of 1193 per million population [5]. The under-recognition and treatment of CKD in its earlier stages and the increasing prevalence of risk factors associated with CKD are implicated in high ESKD rates [8]. Appropriate screening for, monitoring and treatment of certain types of CKD can prevent or delay progression to ESKD. Understanding the geographic variations in prevalence informs health services planning.

Unfortunately, information about the incidence and prevalence of earlier stages of CKD in the general population is limited. Estimates of CKD prevalence in Canada range from 10 to 15%, representing approximately 3 million affected adults [2]. Prevalence rates of CKD across Europe, Asia, North America and Australia range between 2.5 and 11.2% [3] and are highest among low to middle income countries [4]. ESKD represents a small fraction of the total CKD population, with early CKD affecting 50 times more individuals than ESKD [6]. Determining patients who are at greater risk of progression to ESKD is an important aspect of CKD surveillance.

In this study, we propose a novel methodologic approach by combining both laboratory and administrative health data to monitor CKD prevalence. Combining these types of data with novel methods to calculate prevalence could overcome the challenges of the low sensitivity of administrative data. The aims of this study are to: a) develop the Manitoba CKD cohort from a wide range of administrative health databases including medical claims, hospitalization records, prescriptions and laboratory data; b) estimate the CKD prevalence in the province of Manitoba using all sources of data and a capture-recapture method; c) determine the percentage of cases who are at highest risk for progression to ESKD; and d) determine rates of comorbid health conditions among people identified in the CKD cohort.

Figure 2 illustrates how the cohort was created. The total number of Manitoba adults (18 years and older) with CKD found in all databases was 55,876. Of these, 18,342 were identified using administrative health data, 27,393 were found in the laboratory data, and 10,141 people were found in both databases. Table 2 shows the characteristics of the Manitoba CKD Cohort (n = 55, 876). We note that these characteristics differ from the total Manitoba population (n = 991,823). More women than men were captured in the CKD cohort. Over half of CKD cases were 65 years and older. When comparing the percentages of people residing in the rural health regions and the main urban health region, we note that CKD cases in some rural regions appear to be underrepresented.

This study describes the development of the Manitoba CKD Cohort using a combination of administrative health and laboratory data, as well as how adult CKD prevalence was estimated. We found that the CKD prevalence was 5.6%, using the standard method and 10.6% using only people with laboratory data. Using the capture-recapture method, CKD prevalence was also estimated at 10.6% which is in line with previous studies [2]. Of the identified adult CKD cases, 46% were at high risk of progression to ESKD and 41% were at low risk. The remaining 13% did not have any laboratory data and were therefore not categorized by risk. This study also found the expected high rates of comorbid health conditions among adults with CKD, which increased from the low to the high risk cohort, supporting the methodology utilized to assess cases.

The estimated prevalence of 10.6% found in two of the methods used supports the face validity of our approach, although given that ESKD rates in Manitoba are amongst the highest in Canada, these may be underestimates. In a national study, using the Canadian Health Measures survey, Arora et al. [2] found that the prevalence of CKD in Canadian adults ranged from 10 to 15%. Similarly, other investigators, reported CKD rates ranging between 2.5 and 11% across Europe, Asia and North America, and found CKD rates ranging from 4.7 to 33% in low- to middle-income countries. Our results suggest that CKD rates in Manitoba may be at the higher end of the range for high-income countries.

The burden of other health conditions in our CKD cohort is much higher than the provincial average for all the indicators we examined [20]. In the high-risk CKD group alone, the rate of stroke was over 14 times higher than the Manitoba average in 2011/12, and the prevalence of diabetes was over five times higher. Previous studies have found that comorbidities are common in CKD, even in the early stages of the disease and that these comorbidities are associated with increased treatment burden and poorer quality of life [21]. In addition, we found a trend of increasing comorbidity with increasing risk of progression. Previous research shows that rates of comorbid diseases at the CKD stages 3–5 are double the rates at stages 1–2 [2, 22]. Go, Chertow, Fan et al., [23] in a large epidemiologic study, found a graded association between a reduced eGFR and the risk of death and cardiovascular events. A meta-analysis reported that the risk of myocardial infarction increased with lower eGFRs [24].

Our study enabled us to capture individuals through the health care system, who may be difficult to reach in screening/surveillance studies. This allowed us to evaluate the geographical distribution and social factors associated with CKD. Our findings suggest that CKD is not equally distributed across geographic regions and socioeconomic status. The CKD rates increase with decreases in income. We also observed that the highest rates of CKD in remote communities. These remote communities are largely populated by Indigenous peoples where living conditions are challenging due to economic conditions, poor water supply and access to affordable food, as well as limited health, social and recreational services. These findings are consistent with previous research. A recent review found that socially disadvantaged CKD patients had poorer access to health services, and higher rates of cardiovascular events and mortality than more advantaged patients [25]. Despite Canada’s universal healthcare system, people living in poverty and in remote communities, face barriers to accessing early intervention strategies and treatments that are required to prevent and manage CKD. Improving living conditions and ensuring that economic and social resources are available throughout the province would potentially decrease the development of CKD and other chronic diseases. While there are no simple solutions to reducing poverty, some existing strategies have demonstrated improved outcomes [26, 27].

Estimating CKD prevalence has proven to be challenging because the disease is typically without symptoms in the early stages, general population screening is not currently recommended and vulnerable populations at risk may not present for opportunistic screening even if it is offered. Given that survey respondents might be unaware of indicators of kidney disease, health questionnaires are problematic, and incur considerable cost and effort to collect the information. Remote and isolated regions are often not included in large surveys due to lack of infrastructure such as telephones and roads.

Epidemiological studies have relied on either laboratory testing or administrative health data to estimate population prevalence. Arora and colleagues [2] collected health information as well as laboratory tests required to identify CKD cases, from a representative sample of 3689 respondents across Canada. Laboratory tests to detect CKD including proteinuria and eGFR, can not only determine the presence of CKD, but also the risk of the disease progressing to ESKD. Specifically, by categorizing these tests, individuals can be stratified into low risk, moderately increased risk, high risk, and very high risk for progression to ESKD [14, 28‐33]. Administrative databases can be an additional tool to overcome some of the challenges related to cost, time and reaching affected populations. In Alberta for example, a series of definitions for CKD using medical claims and hospitalizations based on the province’s health system were compared to a gold standard [13]. Despite using a longer period, the study found that the definition had 23% sensitivity and 96% specificity. These results indicate that using administrative data to estimate CKD prevalence tends to underreport the true rates and requires validation with population-based laboratory data or large-scale screening initiatives.

In our study, we found that many cases of CKD were not identified through the administrative health data, suggesting that these CKD cases may go undetected and undiagnosed. Given the high prevalence of CKD, it is imperative that primary care physicians conduct routine health checks for at-risk populations. The KDIGO clinical guidelines for CKD [14] and the Canadian Diabetes Association guidelines [34] include recommendations for lifestyle counselling, control of blood sugar and hypertension and avoidance of nephrotoxic substances. Early identification of people at greater risk for progressing to ESKD provides the opportunity for lifestyle counselling to address risk factors and treatments to slow the progression of the disease. Clinical care pathways are available to guide primary care practitioners in the treatment of CKD patients [35]. Furthermore, there is opportunity for increased knowledge translation to ensure that all care practitioners are aware of these guidelines and have access to them in their practices. To ensure that remote communities have access to primary and renal healthcare, alternative models of care should be considered, include increasing recruitment of healthcare providers and using technology to link remote areas to specialized services in larger urban areas. It is important to develop a rigorous evaluation framework to monitor changes in the prevalence of ESKD and high-risk CKD over time in order to increase our understanding of the effectiveness of established screening, surveillance and intervention strategies and shed light on how to improve them.

This study has demonstrated the value of using of innovative methods to estimate CKD prevalence by taking advantage of the overlap between administrative and laboratory datasets. The prevalence estimated by the capture-recapture method is consistent with epidemiologic studies and with the estimate calculated using the laboratory data only. This method has previously been utilized for estimating prevalence of diseases such as acute hepatitis A, diabetes, spina bifida and infants’ congenital anomaly [36]. The prevalence by the capture-recapture method may be an underestimation. Two assumptions are required when using the capture-recapture method: that the dataset includes individual identifiers and that one list does not affect the chance of being on the other list. The second assumption may not be met, because laboratory reports and physician claims are likely related.

Chronic kidney disease (CKD) is a health issue of increasing worldwide importance. Utilizing a combination of administrative health and laboratory data, this study found high CKD rates in Manitoba, with a large proportion at risk for progressing to ESKD. Given the high rates of comorbidity, it is important to have a comprehensive public health strategy that encompasses a range of interrelated chronic diseases. Our methodology may be well suited in the creation of passive CKD surveillance systems to target patients who may benefit from early intervention to prevent progression to more advanced forms of CKD and ESKD.