Non-adherence with ACE inhibitor treatment is common in heart failure and can be detected by routine serum ACE activity assays

Objective-To assess whether serum angiotensin converting enzyme (ACE) activ ity during routine clinical practice accurately reflects patient adherence to ACE inhibitor treatment for chronic heart failure (CHF). Design-Retrospective assessment of ACE inhibitor adherence and serum ACE ac tivity measurements. Setting-Teaching hospital outpatient department Patients and interventions-During 1994-95, serum ACE was measured in 73 CHF patients who were routinely attending the heart failure clinic at Ninewell s Hospital. At the same time, the medicines monitoring unit collected data on whether and when prescriptions for ACE inhibitors were redeemed at commu nity pharmacies, which enabled each patient's adherence over a prolonged pe riod to be assessed. Main outcome measures-Routine collected serum ACE measurements were correla ted with measured adherence with ACE inhibitor treatment. Results-In total, 18% of CHF patients appeared to exhibit < 70% adherence w ith their ACE inhibitor treatment with 34% exhibiting less than 85% adheren ce and 58% exhibiting < 100% adherence. A serum ACE activity of > 12 u/l ga ve 91% positive predictive accuracy that the patient was < 100% adherent wi th their ACE inhibitor treatment. At the other extreme, a serum ACE < 6.5 u /l gave 81% positive predictive accuracy that the patient was > 85% adheren t with ACE inhibitor treatment. Conclusions-Non-adherence with ACE inhibitor treatment was found to be comm on in patients with CHE The simple, inexpensive test of serum ACE activity can be used in CHF patients to identify many, although not all, non-adheren t patients so that adherence enhancing strategies can be targeted towards t hem. Further work is clearly required to explore the precise clinical use o f this promising test.