Accurate reporting of adherence to inhaled therapies in adults with cystic fibrosis: methods to calculate normative adherence

Abstract

BackgroundPreventative inhaled treatments in cystic fibrosis will only be effective in maintaining lung health if used appropriately. An accurate adherence index should therefore reflect treatment effectiveness, but the standard method of reporting adherence, that is, as a percentage of the agreed regimen between clinicians and people with cystic fibrosis, does not account for the appropriateness of the treatment regimen. We describe two different indices of inhaled therapy adherence for adults with cystic fibrosis which take into account effectiveness, that is, “simple” and “sophisticated” normative adherence.Methods to calculate normative adherenceDenominator adjustment involves fixing a minimum appropriate value based on the recommended therapy given a person’s characteristics. For simple normative adherence, the denominator is determined by the person’s Pseudomonas status. For sophisticated normative adherence, the denominator is determined by the person’s Pseudomonas status and history of pulmonary exacerbations over the previous year. Numerator adjustment involves capping the daily maximum inhaled therapy use at 100% so that medication overuse does not artificially inflate the adherence level.Three illustrative casesCase A is an example of inhaled therapy under prescription based on Pseudomonas status resulting in lower simple normative adherence compared to unadjusted adherence. Case B is an example of inhaled therapy under-prescription based on previous exacerbation history resulting in lower sophisticated normative adherence compared to unadjusted adherence and simple normative adherence. Case C is an example of nebulizer overuse exaggerating the magnitude of unadjusted adherence.ConclusionDifferent methods of reporting adherence can result in different magnitudes of adherence. We have proposed two methods of standardizing the calculation of adherence which should better reflect treatment effectiveness. The value of these indices can be tested empirically in clinical trials in which there is careful definition of treatment regimens related to key patient characteristics, alongside accurate measurement of health outcomes.

Role of habit in treatment adherence among adults with cystic fibrosis

“…Item scores were then summed to create a scale ranging from 4 (weakest habit) to 20 (strongest habit). Adherence data were downloaded from chipped nebulisers (eTrack) in the 3-month period following the point of recruitment, and calculated as ‘normative adherence’,8 a measure that takes into account a person’s characteristics when defining the minimum required treatment regimen (see online supplementary appendix). Participants were divided into three adherence categories (<50% for low adherence, 50%–79.9% for moderate adherence, ≥80% for high adherence) to mirror the analysis of our earlier Sheffield study 6.…”

Rescue therapy within the UK Cystic Fibrosis Registry: An exploration of predictors of intravenous antibiotic use amongst adults with CF

“…The detection of P. aeruginosa infection would typically prompt the prescription of inhaled antibiotics. However, there may be merit in using long‐term inhaled antibiotics, even when P. aeruginosa is not detected, if there is a history of frequent exacerbations . This is a strategy that has some evidence of success in non‐CF bronchiectasis …”

“…However, there may be merit in using long-term inhaled antibiotics, even when P. aeruginosa is not detected, if there is a history of frequent exacerbations. 45 This is a strategy that has some evidence of success in non-CF bronchiectasis. 46 Our finding highlights potential limitations of FEV 1 as a marker of lung health.…”

An Early Health Economic Analysis of the Potential Cost Effectiveness of an Adherence Intervention to Improve Outcomes for Patients with Cystic Fibrosis

“…These data suggest a lower median adherence rate of 36% in nebulisers that are brought to clinic to be downloaded [7]. It is also important to ensure that estimated adherence rates take into account the patient's clinical status ("normative adherence") and includes both nebulisers brought to clinic and the more difficult to obtain nebulisers left at home; UK data reported by Hoo et al suggest that when all nebulised devices are included, normative adherence in adult clinics may be as low as 33% [8].…”