Changing BP targets: Evidence vs opinion
Clinical practice is an art guided by good science, and clinical practice guideline (CPG) is meant to guide in integrating the art and science of clinical practice for the long-term benefits of patients, said Dr Abdul Rashid Abdul Rahman, a consultant cardiovascular physician at An-Nur Specialist Hospital in Bangi, Malaysia, during the 13th Asian-Pacific Congress of Hypertension (APCH) held in Singapore.
“CPG is a document authored collectively by individuals who individually disagreed with what was written,” Rahman amused the crowd with a humour quote.
Although a general blood pressure (BP) target of <140/90 mm Hg is recommended for all patients with hypertension by major international bodies including AHA*, ESC/ESH**, JNC8***, ASH/ISH#, and NICE##, there have been some discords on the ideal BP targets for specific groups of hypertensive patients such as those with coronary artery disease, diabetes, who are elderly, or who have previous cerebrovascular accident, he noted.
One of the reasons for the discordance in existing recommendations lies in the choice of evidence, ie, randomized controlled trials (RCTs) on which the recommendations are based on. Among the different committees, the number and types of major RCTs chosen for setting recommendations differ greatly, observed Rahman. For instance, the ACCOMPLISH trial was not mentioned in the NICE guideline, while major trials like ASCOT and HOPE were not quoted in the ASH/ISH and JNC8 guidelines.
Not only does the choice of evidence differ, the interpretation of the evidence may also differ among the panellists, which may contribute to the lack of agreements between guidelines, according to Rahman. HYVET, a major trial considered to bear important evidence for elderly patients with hypertension was referenced in both the ESC/ESH and ASH/ISH guidelines (although it was left out in the NICE guideline). However, a BP target of <150/90 mm Hg was recommended for patients aged >60 years in the ESC/ESH guideline but the target age group was >80 years in the ASH/ISH guideline.
“How stringent are we with using the evidence?” asked Rahman. “Do we include only hypertension-dedicated trials or RCTs with adequately powered clinical outcomes? Do we include only primary outcome trials or meta analyses of RCTs?”
“When it comes to treatment recommendation, we should only stick to hypothesis-testing studies (not subanalysis or post hoc analysis).”
Besides, RCTs-based guidelines do pose some limitations in terms of the generalizability to the real-world scenario, he added, alluding to the frequent exclusion of complicated patients in RCTs, compliance rates which were often too good, and events rates which were too low compared with those observed in daily practice. Also, generalizability to older or higher-risk patients was questionable while Asian patients were rarely studied in RCTs.
Bridging the gaps
“Gaps existing within the current CPG should be addressed by well-thought out research,” said Rahman. “We need consensus on how to choose evidence which matters, how to interpret evidence, be guided by results from clinically important surrogate endpoints in the absence of RCTs, and conduct definitive RCTs to address specific gaps.”
According to the NICE 2011 report, research questions that remain to be answered include out-of-office BP monitoring, method of assessing lifetime cardiovascular risk in those aged <40 years, and the optimal systolic BP target.
“Psychosocial and behavioural aspects of care must not be neglected,” reminded Rahman, noting that recommendations on lifestyle interventions can be anticipated in the upcoming NICE guideline due in 2018.