Clinical guideline woes could be fixed by “evidence surveillance”

Risk factors

By Nicola Garrett

21 Aug 2019

The number of adults classified as hypertensive would have almost doubled if Australia had adopted the most recent US hypertension guidelines, an expert says.

Delivering an address on hypertension guidelines – the US vs the rest of the world, senior director of the Baker Heart and Diabetes Institute Professor Gary Jennings said the move by the ACC/AHA to define hypertension as a blood pressure of ≥130/80 mm Hg rather than 140/90 mm Hg had caused much controversy across the globe. 

“Some would say this is a fairly small difference, after all blood pressure can vary by 10 mmg Hg from one measurement to another and between one technique and another,” he told delegates.

“But we do know from epidemiology that the 10 mmg Hg increase across the population is associated with double the cardiovascular mortality and we also know that the upper percentiles of BP track from childhood so the implication of a particular BP might be quite different in the young compared to older people…at a population level the consequences are huge,” he said. 

The stronger recommendations for more aggressive therapies and lower thresholds in the US guidelines were largely derived from the SPRINT study which showed that targeting systolic BP at 120 mmg Hg was associated with a reduction in cardiovascular outcomes and total mortality, Professor Jennings explained. 

On this point, Australia had taken a similar line to Canada by taking the view that it was not certain if the results were generalisable beyond the actual SPRINT population. 

“In a very careful way,  we’ve said if you have patients who fit the SPRINT criteria and you’re doing everything else the same way as SPRINT methodology then there is a case for going for more intensive blood pressure goals even down to 120 mmg Hg systolic,” he told delegates.

Clinical guidelines need to be living documents

Professor Jennings said that one of the many issues with clinical guidelines is that they attempt to go straight from evidence to practice. 

“The problem is that the evidence comes in waves but when we write a guideline we stop the clock,” he said. 

There were also often many underrepresented populations in the trials used to support guidelines as well as different approaches in the way professional organisations appointed to their guideline committees.

“The seventh report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC7) used clinical experts in hypertension… but the AHA/ACC/CDC had a different approach where they excluded people with conflicts of interest and consequently had very few people that had direct involvement in the hypertension community,” he explained. 

“So in a perverse sort of way people make a choice between taking a group that has no conflicts of interest and are not involved in the field compared to those who are potentially conflicted but perhaps know a lot about it.” 

According to Professor Jennings the answer to these issues was the creation of living guidelines, that begins with an extensive and complete evidence review but are then constantly updated.  

“The stroke community has taken the lead on this in Australia… there are platforms that are available that support this and I think this is the way that we will see things happening in the future but we’re a long way from that now,” he said.

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