Sunday, May 23, 2010

Hypertension, In-Home BP Monitoring, Web-Based Reporting, Phamacists and Press Releases: Read the Studies for Yourself

Sometimes the Disease Management Care Blog fancies itself as a virtual "journal club" that simultaneously combines updates on medical research with healthy levels of skepticism about the underlying science. It's a useful way to think through much of the spin that can clutter breaking news about medical advances. Given our mainstream media's spotty track record when it comes to reporting and interpreting medical news, wary journal club approaches are needed more than ever when it comes to uncovering the facts and only the facts.

Case in point? Check out this Kaiser - Microsoft press release touting a "50%" improvement in blood pressure control thanks to "in-home BP monitors and web-based reporting tools that connect clinicians and patients via the internet." The study of "348 patients" was presented at an American Heart Association meeting.

It goes on to say:

At the start of the study, the average systolic blood pressure was 149 mm Hg in the home monitoring group and 145 mm Hg in the usual care group. At six months, patients in the home monitoring group were 50 percent more likely to have their blood pressure controlled to healthy levels compared to the usual care group. Similarly, a significantly greater decrease in systolic blood pressure at six months occurred in the home monitoring group (-21 mm Hg) versus the usual care group (-9 mm Hg).

The DMCB thought this sounded quite impressive, so it pulled the AHA meeting abstracts and went to page 82. According to the report, "A Pharmacist-led, AHA Heart 360 supported Home Blood Pressure Monitoring Program Improves Blood Control in Patients with Uncontrolled Hypertension," the experiment involved a total of 353 (not 348) hypertensive patients who agreed to be randomly assigned to usual care (N=174) or an intervention group (N=179). The intervention really involved a pharmacist-led program that adjusted the patients' medications in response to home BP readings that were uploaded into a personal health record HealthVault.

Six months later, data was available on 125 of the usual care patients and 120 of the intervention patients. 47 of the 125 patients, or 38%, in the usual care group vs. 69 of 120, or 58%, of the intervention patients reached target blood pressure levels. This difference turned out to be statistically significant. After some statistical adjustment, the 20% absolute advantage (58% minus 38%), works out to represent an approximate "50%" relative advantage. In other words, if a Kaiser pharmacist is adjusting your blood pressure pills, you're 1.5 times more likely to get your blood pressure under control compared to usual care.

Or does it? The trial started out with 353 patients but ended with only 245 - which is about a 30% drop out rate. A more conservative calculation would include the drop outs and assume none of them got their blood pressure under control. Accordingly, 47 of 174 or 27% of the usual care group achieved blood pressure control while 69 of the 179 or 38% of the pharmacist led group did so. That's a more modest absolute improvement of 11% or a 1.4 relative likelihood of control. The DMCB went to this web site to do a quick chi square and thinks the results had a more modest yet still statistically significant p value of .03.

So what does the DMCB think?

Never take a press release's word for it: always go to the original report and read it for yourself. In this instance, there were two important features that were not stressed in the press release:

1. The secret sauce behind study was really being "pharmacist led" (the title of the study), not home based monitoring and web-based reporting. In that context, this isn't really all that new: it's abundantly clear that non physicians can improve care quality. To sort out the added value of the Kaiser-Microsoft alliance, we'd need a trial that compares pharmacist-directed care using the old fashioned telephone vs. pharmacists using a web-based personal health record.

2. Learn to look at the numbers: in this instance, a casual read uncovered a 30% drop out rate. By focusing only on the patients that remained in the study at 6 months, the authors cast a more favorable light on their success rates. In addition the "1.5" relative likelihood of improvement is technically correct but of less use to doctors, who have to worry about the patients who may not keep appointments. They're more interested in the 11% absolute improvement rate.

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