Research highlights – 5 August 2011

Research questions“Research highlights” is a weekly round-up of research papers appearing in the print BMJ. We start off with this week’s research questions, before providing more detail on some individual research papers and accompanying articles.

Cutting proteinuria in patients on high dose ACE inhibitors
The BMJ doesn’t receive many crossover trials, but here’s one. It addresses what the editors thought to be an interesting and practical question about the comparative effectiveness of a dietary intervention versus polypharmacy. (And the authors adopted a particularly provocative acronym, the HONEST (HOlland NEphrology STudy) group, but that’s not why we published the study.)

Patients with chronic kidney disease need to keep hypertension and proteinuria at bay, but simply taking a high dose angiotensin converting enzyme (ACE) inhibitor doesn’t usually tackle the proteinuria adequately. So Maartje Slagman and colleagues enrolled Dutch outpatients with non-diabetic renal disease who were already taking an ACE inhibitor at the maximum dose. All 52 patients had four treatment periods of six weeks in which they received, in random order, angiotensin receptor blockade or placebo, each combined with, consecutively, a low sodium diet and a regular sodium diet. Dietary sodium restriction to a level recommended in guidelines and reinforced through individual counselling by dieticians was more effective than dual drug blockade for reducing proteinuria and blood pressure.

Just 52 patients may seem an awfully small sample size but—as another paper, co-authored by the BMJ’s senior statistics editor, Doug Altman, explains—“each participant [in a crossover trial] is able to act as his or her own control and permits between and within group comparisons . . . when the new treatment [is] a slight modification to the standard…there is likely to be a positive correlation in the responses to the new and old treatments making the crossover design ideal. Crossover studies are most appropriate in studies where the effects of the treatment(s) are short-lived and reversible and are best suited to trials related to symptomatic but chronic conditions or diseases” (Trials 2009,10:27, doi:10.1186/1745-6215-10-27).

Calorie labelling of fast food
In response to the obesity epidemic in its citizens, New York City approved a regulation requiring chain restaurants to provide calorie information prominently on all menus and item tags, and this regulation became effective in March 2008.  To investigate whether this measure had any effect, surveys of customers’ lunchtime purchases from fast food outlets were conducted in spring 2007 and spring 2009 (one year before and nine months after implementation of the regulation).  Tamara Dumanovsky and colleagues now report their findings.

No overall decline in energy content of purchases was observed, but the 15% of customers who actually bothered to read the calorie information reduced the energy content of their lunch by an average of 106 kcal, enough to make a real difference to body weight if sustained. The study has generated quite a bit of media publicity but with decidedly mixed reaction, with some stories claiming it shows the regulation to have been an abject failure while others have proclaimed it a triumphant success.

In her linked editorial, Susan Jebbs seems to think the results are about as good as could be expected and concludes: “Calorie labelling will help consumers make an informed choice about what they eat, but sustained improvements in the nation’s diet will require a transformation of the food supply too.”

Impact of CYP2C19 variant genotypes on clinical efficacy of antiplatelet treatment with clopidogrel
The efficacy of antiplatelet treatment with clopidogrel is thought to be affected by the patient’s genotype, and current guidelines advise taking this into account when deciding on antiplatelet treatment. But a systematic review and meta-analysis by Tim Bauer and colleagues found that the available evidence does not support this practice.

The health risks and benefits of cycling in urban environments compared with car use
David Rojas-Rueda and colleagues studied a public bike sharing scheme in Barcelona, Spain, and report that it was a good thing for both individual and public health.

Oxytocin bolus versus oxytocin bolus and infusion for control of blood loss at elective caesarean section
The addition of an oxytocin infusion after caesarean delivery reduces the need for additional uterotonic agents, but does not affect the overall occurrence of major obstetric haemorrhage, say Sharon Sheehan and colleagues.