Using nationally representative data, this study assessed coverage of individual-based primary prevention strategies involving early detection and management of risk factors for CVD in two LMIC countries in Asia.
The study revealed key CVD risk factors already at alarming levels, with hypertension in particular emerging as a major public health concern. This high prevalence of risk factors warrants aggressive population-wide strategies such as public awareness campaigns and appropriate legislation and policy measures to alter societal norms relating to dietary salt intake, tobacco smoking and physical inactivity [27
]. Individual-based primary prevention using medical and non-medical measures to reduce risk factors in high-risk persons also needs to be scaled-up to complement population-wide measures.
Timely detection of underlying risk factors, a critical component of the individual-based primary prevention strategies, emerged as a major challenge. No formal guidelines for universal, targeted or opportunistic screening for CVD risk factors existed at the time of the surveys in both countries, though both prioritize early detection of NCDs in current national policy and program documents [16
The results suggest that an improved proportion of cases might be detected by targeted testing. For example, while in Cambodia only 16.5% of 35-64 year old population reported previous testing for blood sugar and yet 50.3% of total diabetic cases were previously diagnosed. Indeed, universal screening may not be feasible in many LMIC: evidence-based guidelines for opportunistic screening of high-risk population groups as identified based on epidemiological profile may be the first step, although poor overall health service utilization may limit coverage [31
]. The frequent co-existence in individuals of several risk factors justifies strategies/guidelines for concurrent screening for multiple risk factors, an approach that also allows assessment of the absolute global risk of developing CVD in the next five to ten years--the recommended approach for making treatment decisions as discussed later [33
The treatment gap in each country comprises those who are untreated because they are as yet undiagnosed, plus the proportion of individuals who are untreated despite previous diagnosis. In the absence of any follow-up questions, it is hard to identify the reasons for lack of treatment in these previously diagnosed hypertensives and diabetics, which may be both supply and demand related: due to factors related to difficulties in accessing or paying for treatment, and in some cases personal attitudes or preferences. A substantial treatment gap amongst the previously diagnosed population suggests that any plans to improve early diagnosis must be accompanied by increased provision, accessibility and affordability of treatment.
Approximately 14% and 17% of total of population with raised blood pressure and 10% and 26% of diabetics in Cambodia and Mongolia, respectively, reported receiving non-medical treatment alone. Such high proportions may reflect national guidelines that encourage utilization of non-medical lifestyle treatments in patients below recommended thresholds for initiation of medical treatments. But they may also in part reflect the reliance on non-medical therapies in a subgroup of patients who cannot afford or access medical treatments.
Although guidance on diagnostic thresholds for initiating medical treatment may vary, non-medical interventions are recommended in all individuals at the diagnostic threshold used in this study [33
]. In Mongolia 14% of hypertensives reported receiving medical, but no non-medical treatments raising concerns about clinical practice. It appears that appropriate lifestyle advice that can improve management is not reaching many of these people.
The results suggest that diagnosis or initiation of treatment does not ensure effective disease management. Point estimates indicate worrisome levels of uncontrolled blood pressure and blood glucose among people on treatment and poor life-style advice levels amongst subgroups especially in need.
Implications for service development
Our findings for diagnosis gap and treatment coverage and quality are in line with other research that has drawn attention to suboptimal diagnosis and management of NCD risk factors. For example, some 70% of diabetics in seven countries in Europe, Asia and North and South America were assessed as failing to attain recommended blood sugar levels [12
]. To reduce CVD mortality, a key goal of primary prevention strategies is to achieve a reasonable level of control of these risk factors. For example, one of the national objectives under Healthy People 2010 initiative in USA includes controlling blood pressure in 50% of all individuals with hypertension [10
This study suggests that in Cambodia and Mongolia only about a quarter of all hypertension and less than a quarter of all diabetes is adequately controlled. Thus improvement in primary prevention strategies will require multifaceted efforts to improve detection and diagnosis, treatment of those diagnosed, and the quality of treatment among those who are treated In addition, our findings suggest improvements can be made in optimal use of non-medical therapies.
Finally, the very high prevalence of risk factors as defined at the cut-offs levels used for each risk factor may imply need for substantial increase in health financing to provide drug treatment. Global absolute CVD risk assessment based on levels of multiple risk factors may be used to prioritize people with higher overall CVD risk for drug treatment, while those with lower overall risk may be followed-up with systematic life-style interventions. WHO and International Society for Hypertension has published cardiovascular risk prediction charts for all the fourteen WHO epidemiological sub-regions that can be used by physicians or non-physicians in low-resource settings to estimate 10-year risk of a fatal or non-fatal cardiovascular event [33
]. Recent research has suggested this approach offers substantial cost-saving in drug treatments [35
]. Appropriate screening strategies will still be required for early identification of people with moderate to high absolute global CVD risk, but to date none of the countries have formally introduced clinical guidelines either for screening or treatment based on absolute CVD risk assessment, though Mongolia is in the process of developing these guidelines.
The study has limitations that must be acknowledged. For example, due to the surveys' cross-sectional nature, whereas guidelines recommend that diagnosis should only be made on the basis of raised blood pressure sustained over time, the study diagnoses of hypertension are based upon multiple measurements at a single visit and thus may not be sufficient for a confirmed diagnosis or to assess the adequacy of control in individuals [16
]. There may be inter-investigator variations in measurement that were not assessed in the survey and hence were not taken into account. The advice to refrain from the taking of diabetes medications on the morning of the blood tests may have delayed medication for some hours and affected readings in some participants. Adherence these and to fasting instructions is unknown. While the literature is consistent on suitability of capillary whole blood for screening of diabetes in population based surveys, the cut-off used to diagnose diabetes for capillary blood versus venous plasma is still debatable [23
]. In the absence of any clear national guidelines in either of these countries, we used the most-commonly used cut-offs reported in international literature and guidelines. Measures of prevalence, diagnosis and treatment gap will vary greatly based on the diagnostic cut-off for hypertension and diabetes,, though this methodology will still be appropriate to assess the trends in these indicators over time if similar measurement methods and diagnostic cut-offs are used. Finally, the study does not capture the complete disease burden that health systems may face, due to exclusion of population aged over 65, which may have much higher disease burden.
Implications for future surveys/research to monitor response to NCDs
With regards to self-report of previous testing, it was not possible to ascertain whether individuals were tested previously as part of formal, opportunistic or universal screening programs or were simply tested when they sought services on experiencing symptoms. Nor can the source of testing be discerned: whether public or private or whether in primary or secondary care. Inclusion of questions on context of testing in future surveys may help to evaluate early detection strategies as more countries scale up NCD early diagnosis and care programs. Additional questions on adherence to treatment, cost and affordability of treatment and source of treatment may be included to distinguish and estimate the demand and supply-side factors affecting the treatment coverage. We were unable to examine the primary prevention of hypercholesterolemia due to lack of medical history for prior diagnosis and treatment. Considering the prominence given to high cholesterol levels in determining absolute CVD risk, the medical history for hypercholesterolemia may be included in future surveys.