Methodological Issues in Measuring Adherence to Antimalaria Drugs

2. Methodological Issues in Measuring Adherence to Antimalaria Drugs Irene A. Agyepong, Evelyn K. Ansah, Margaret Gyapong, David Evans, Guy Barnish

3. Challenging Methodological Issues • Defining Adherence • Collecting data to enable measurement of adherence • Analyzing the data • Relating the data to other variables (identification, understanding and measurement of other variables) • In the rest of the presentation each issue above is discussed a little more as well as: • How it was addressed in our study • The strengths and weaknesses of how it was addressed

4. Defining “adherence” • Adherence – Comparing how the patient took the drug with how they were supposed to take it • Doing exactly what the prescriber or dispenser wrote or said – Ethical and Technical Issues • In measuring adherence is it relevant or irrelevant whether the prescription is technically “correct” or not? • What do you do when the prescription is technically “incorrect” • What do you do when the patient happens to know or be told the “correct” dose by another person and adheres to that?

5. Defining “adherence” • Several possibilities for defining and therefore measuring adherence • Example of Categories • Strict Full Adherence – Patient takes the exact dose prescribed everyday for the full duration of treatment. A higher or a lower dose taken on any one day leads to the patient being classified as non adherent • Minimum Daily Adherence – A sub-optimal dose on any one day is regarded as non adherence. However if the client takes a little more than the recommended dose e.g. 5 tablets instead of 4, they are still registered as adherent • Other category possibilities e.g. MTA

6. Collecting the Data • Ideally to be sure you have 100% accuracy in recording how the patient took the drug you need to observe the process • However being there to observe on a daily basis is expensive & introduces bias related to ‘instrumentation’ • The presence of the observer each time a dose is due to be taken becomes an intervention that could in itself increase adherence • Realism vs. precision i.e. How strict to be on detail (e.g. 8 hrly vs 3 times daily)

7. Collecting the data • We settled for data collection using one visit to the home within 24 hours after the last dose was supposed to have been taken • This was feasible since only a 3 day recall was involved • The data collector took the clients statement of how they took the drug as a fact, but also crosschecked by examining the bottle or package to see if anything was left and compared it to what was supposed to have been taken

8. Collecting the data • The problems and the expense involved in tracking clients to their homes in the developing country setting of no house numbers, street names, telephone numbers etc • The problem of syrups • A tablet is pre-measured so to speak • But what do you do about the definition of a teaspoon in the home in a situation where child caretakers are not given measures at the clinic with the syrups • Is a mother who gave “one teaspoon” daily non adherent because her understanding of a teaspoon is a dessert spoon or a coffee spoon or the cover of the bottle?

9. Analyzing the data • Need to simplify and quantify definitions for statistical analysis of data • Manual comparison of prescription given and the way the drug was taken to code adherence • Coding and entry of codes • Strict Full Adherence (SFA yes=1, no=0) • Minimum Daily Adherence (MDA yes=1, no=0)

10. Relating the data to other variables • Written prescription vs verbal instructions vs labeling on bottle – do they tally • Prescriber and dispenser instructions – do they tally? • In our initial study they tallied over 95% and we just took dispenser instructions • Issues of measurement coming up in the current qualitative & exploratory study of factors affecting adherence • e.g. quality of communication – what the dispenser said vs. what the client heard, understood & remembered and its influence on adherence

11. Improving adherence measurements in the future • Would daily charting of dose taken and frequency by patients themselves be a workable alternative to recall from memory and what kind of bias might it introduce since it is in itself perhaps an intervention • Especially important to ask in measuring adherence where dosages are more complex than once daily for 3 days as in the case of chloroquine since memory recall will worsen with longer duration and more complex regimens

12. Improving adherence measurements in the future • Possible to agree on certain standard definitions for measurement to make different studies comparable on a core set of variables? • Better understanding, measurement and analysis of factors that affect adherence in the developing country context and development of means of quantifying complex variables like “quality of communication”