LITERATURE REVIEW OF DECISION MODELS FOR DISEASES WITH SHORT-TERM FLUCTUATIONS/EPISODES: The Case of COPD Dr. Orpah Nasimiyu Wavomba

BACKGROUND/INTRODUCTION  Literature review on COPD (Chronic Obstructive Pulmonary Disease). A progressive disease affecting over 200 million people worldwide and responsible for the deaths of millions more.  Scope was on existing economic models and how these models incorporate exacerbations in terms of their costs and utilities. An exacerbation of COPD is defined as an event in the natural course of the disease characterized by a change in the patient's baseline dyspnea, cough, and/or sputum that is beyond normal day-to-day variations; is acute in onset; and may warrant a change in regular medication (GOLD, 2008).

HEALTH ECONOMIC MODELS  Useful in sythesising clinical, economic and quality of life data obtained from epidemiologic and population databases and extrapolating the results to predict future outcomes (Hoogendorn et al., 2011)  Model type depends on disease type. Acute conditions using decision trees whereas chronic conditions utilise Markov models.  COPD being a chronic disease therefore utilizes Markov modeling with associated costs (direct and indirect) and outcomes (for example number of exacerbations avoided, number of hospital days avoided and QALYs) are measured.

EXACERBATIONS  Management of disease related exacerbations present considerable clinical and economic burden to society.  Prevention and associated management of these fluctuations remain treatment goals (Anzueto, 2010).  This is especially due to effects of these events on long-term life expectancy, health related quality of life and disease associated costs.

STUDY SELECTION PROCESS  Involved combing through health databases (EMBASE, MEDLINE, PUBMED, ECONLIT, CINAHL and COCHRANE) and unearthing existing economic model papers on COPD.  Papers were put through a study selection process that included inclusion and exclusion criteria before a final number of papers were identified to be included in the study.

Identification Eligibility Included Screening Records identified through database searching (n=209) MEDLINE n=63, EMBASE n=65, PUBMED n=33, COCHRANE n=39, ECONLIT n=2, CINAHL n=7 Records screened (n = 138) Records after duplicates removed (n = 138) Full text articles assessed for eligibility (n = 49) Records excluded: (n = 89) Not disease area n=45, Not economic evaluation n=26, Not decision model n=18 Full text articles excluded (n = 27) Conference abstracts n=17, Not English language n=1, Non- pharmacological interventions n=5, Methodological papers n=3 Final number of studies included in review (n =22) Additional records identified through forward citation (n =1)

RESULTS  In a nutshell, from the 22 papers analyzed, the incorporation of exacerbations in terms of associated costs and utilities were seen to vary significantly from paper to paper.  This could be attributed significantly (approx. 50%) on the varying definitions of what an exacerbation is ultimately affecting their incorporation in the modeling of the disease.  There was a general consensus on the need for a uniform definition to help patients identify symptoms and seek medical attention earlier thus curbing the need for hospitalization and improving on health outcomes.  For example, should the definition be focused on symptom severity and duration or should it focus on pharmacological management and need for hospitalization.

COPD IN AFRICA  Publications on COPD in sub Saharan Africa are limited and far in between.  WHO predicts that by 2030 it will be the 3 rd leading cause of mortalities in some economic regions.  In fact, in addition to a tangible increase in tobacco smoking in many low to middle income economies and occupational hazards, the use of biomass fuels in cooking and heating has been identified as having a positive casual relationship with the disease in non smoking individuals (Imbaya et al, 2014).  Need for further evidence based research in the area.

HEALTH ECONOMICS RESEARCH  Health economics is a branch of economics concerned with issues related to efficiency, effectiveness, value and behaviour in the production and consumption of health and health care.  Basically, we study the functioning of health care systems and behaviours affecting health. In that way, these studies affect policy and resource allocation decisions.  We are looking at times where a patient centered health care approach is desirable and is indeed attainable with the right resources.