The prevalence of CKD stages 3 to 5 in this adult population who were 30yrs and above, with type 2 diabetes, was 39.0% (95%CI, 34.3–44.2) by eGFR (<60 ml/min/1.73 m2) and 32.7% (95%CI, 32.7–37.4) for albuminuria. Focusing on each CKD-stage, 33.5% were in stage-3, 4.7% in stage-4 and 0.8% in stage-5 in this study. The occurrence of CKD was previously unknown to both the patients and healthcare providers. These stages of CKD are often asymptomatic, so patients do not promptly seek care. The stages are only detected when appropriate tests are done.
The policy of cost-sharing in public health facilities may have limited access to both clinical care and laboratory diagnostic services of the patients who could not afford them. This study excluded any patients who had recently been discharged from hospital; therefore, the prevalence reported is an underestimate.
The meta-analysis of studies on diabetes kidney disease in sub-Saharan Africa by Noubiap JJ et al (14) gave a summary on methods used and characteristics of the patients involved in those studies, mentioning some shortcomings that limited adequate comparability. Several of those studies included patients with type 1 and 2 diabetes, conditions with fairly divergent time paths towards evolution of kidney disease, even when risk factors may be common.
In this study, we discuss the prevalence CKD stages 3 to 5 in context of its magnitude, clinical significance, opportunities of case-finding and implication to care needs.
Studies to determine the prevalence of CKD stages 3 to 5 and/or albuminuria in patients with type 2 diabetes in sub-Saharan Africa have found a wide range of figures. Our own study on patients with type 2 diabetes for less than 2 years but relatively younger, in a tertiary hospital, found 26% had albuminuria.(15) Ngassa et al, in S. Africa found 33.6% of their patients had proteinuria and 17.3% had CKD of stages 3, 4 and 5 (eGFR<60 ml/minute/1.73m2), aggregated for both type 1 and 2 diabetes.(16) The prevalence of CKD in patients with type 2 diabetes was 41.1% in a Nigerian study.(17) Advanced CKD, of eGFR<60 ml/min/1.73 m2, was found in 18.2% and 23.8% of subjects with diabetes using the MDRD and Cockcroft-Gault (C-G) equations respectively, in an Ethiopian study,(18) demonstrating that the equation used to calculate eGFR may also explain variations in prevalence. Two studies on patients with type 1 and type 2 diabetes were conducted in two different places in Tanzania: Janmohamed et al, found 79.9% had albuminuria and 83.7% had CKD (eGFR<60 ml/minute/1.73m2), (19) while in Lutale et al, 17% had albuminuria and 22% had CKD stages 3 to 5. (20) Their methods of determining proteinuria were different and target populations varied in ages, duration of diabetes and other characteristics. The prevalence of CKD in studies in sub-Saharan Africa is relatively high, in spite of the differences in patient characteristics within diabetes and the methods used to determine the eGFR. However, CKD and albuminuria still exhibit common determinants of aging, hypertension, poor glycaemic control and socio-economic challenges in studies that evaluated them. This study did not show glycaemic control as a significant predictor of chronic kidney disease, likely because of its cross-sectional design.
Screening and case finding for CKD in patients with diabetes is important because early stage disease can be managed to delay progression. (21, 22)
The potential cost of morbidity and mortality from progressive CKD in type 2 diabetes is enormous, barely affordable in resource-scarce settings. This is much more important in high-risk individuals where the factors that initiate CKD, are often also the drivers of CKD progression.
Renal functions do improve when therapeutic targets are attained, (23) therefore CKD and its drivers of progressions should be actively sought for in patients attending general diabetes clinics as standard of care. Modelling of data on screening strategies has demonstrated the cost-effectiveness of screening for CKD and optimally managing hypertension. (24)
Our study showed that age above 50 years, (and age as a continuous variable), was associated with having CKD/KDIGO stages 3 to 5. In addition, living with diabetes for 5 years and more, increased the odds of having advanced CKD stages. Similarly, other studies have demonstrated that aging is associated with deteriorating kidney function (25, 26), and long duration of diabetes compounds it. (27) These parameters are easily determined in clinics and should assist in stratifying our patients into risk categories during routine follow-up for case-finding, especially in patients who also have other risk factors like hypertension, chronic poor glycaemic control and cigarette-smoking. Therefore, sophisticated and/or costly tests are not necessary for case-finding of chronic kidney disease in routine care.
Hypertension, a modifiable risk factor increased by 3-fold, the odds of having advanced CKD stages in this study. Hypertension causes chronic kidney disease in type 2 diabetes (28, 29, 30, 31, 32) and other cardiovascular events like heart failure (33) and stroke (34, 35) but when hypertension is under control in such subjects who retain normal kidney function, it mitigates the potential for developing CKD. (36, 37) Conversely, poor or insufficient control of hypertension initiates CKD (and causes progression of CKD to more advanced stages). Use of ACEi’s/ARB’s in control of hypertension mitigates renal disease progression. (38, 39, 40, 41) Our study registered 69.0% users of ACEi/ARB agents; however, we did not determine duration of use, doses nor their adherence patterns. Just below a quarter of our study patients with hypertension, at the time of enrolment, had optimal control of the high blood pressure. We have previously documented similar modest proportion of patients with hypertension on type 2 diabetes who achieved optimal Blood Pressure control while on treatment. (42) Another study elsewhere in sub-Saharan Africa (43) also reported similar small proportions, emphasizing that there is urgent need to increase the proportions achieving blood pressure targets.
From this study we infer that diabetes care in the clinic was neither sufficient to achieve optimal control of the modifiable risk factors nor able to detect complications in the patients. These findings suggest that patients with type 2 diabetes for 5-years and more, aged 50 years and above, have hypertension, also are cigarette-smokers and of modest socio-economic capacity should be screened for CKD. Many patients with type 2 diabetes who attend public hospital clinics in sub-Saharan Africa, may look well, but they will need screening for CKD. The WHO document of Wilson and Jungner (44) supported CKD screening amongst patients with type 2 diabetes because it is a public health problem, that early disease is recognizable and screening tests are acceptable to populations, amongst its ten items. Indeed, screening for chronic kidney disease in diabetes has been recommended but in the developed world (45, 46, 47). A review from experts to justify the same for overall CKD screen in sub-Saharan Africa was recently published. They noted that screening for a disease would demand availability of (or access to) treatment and that is our major undoing in sub-Saharan Africa. (48, 49) However, improvement in public health systems should equalize opportunities for access to quality care, in this context, of high-risk diabetic patients like these in our study. The audit part of this study has been published (50). Spot urine test for albuminuria and occasional kidney function test for eGFR are not often done on these patients, as standard of care. Doing these relatively simple tests unmasked very important clinical information which had been missed out before.