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Research Briefs

Put your right knee in . . .
If you need both knees replaced, should you have them done separately (two operations but easier recovery) or together (harder recovery but one operation)? A recent DMS study in the Journal of Bone and Joint Surgery shed light on a factor in the decision. The researchers examined 122,385 Medicare enrollees and found that the adjusted risk of a pulmonary embolism, a blood clot in the lung, is about 80% higher in the three months after a simultaneous procedure than in the three months after a oneknee procedure, which, they wrote, "suggests that the sum of the risks associated with the two operations . . . may equal or exceed the risk of simultaneous total knee replacement."

Mind the gap
Alan Green, M.D., was the lead author of a paper in Schizophrenia Research that compared two different medications for patients who experienced a first episode of psychosis. In the double-blind, two-year, multisite trial, 263 patients were randomly assigned to take either olanzapine or haloperidol. Those in the olanzapine group were less likely to stop taking the drug and more likely to experience remission. "The data," wrote the authors, "suggest some clinical benefits for olanzapine," though they added a cautionary note about side effects.

Take this to heart
Wider use of a new cardiovascular screening test—for a substance called c-reactive protein (CRP) —"doesn't make much sense," according to Steven Woloshin, M.D., and colleagues. DMS researchers reported in the Journal of General Internal Medicine that adding CRP testing to routine assessments would increase the number of Americans eligible for cholesterol-lowering medication by about 2 million if used judiciously and by over 25 million if used broadly—with most of those people being at low risk for heart problems. Doctors should instead focus on treating highrisk patients, the authors argued.

Totally random
A team of Dartmouth researchers compared four different statistical methods for analyzing data in observational studies—that is, studies of patients who have already been treated, rather than randomly assigned to get one or another treatment. Observational studies are less expensive and less cumbersome, but, said the authors in the Journal of the American Medical Association, caution needs to be used in interpreting their findings. They analyzed a single set of data four ways; a method called instrumental variable analysis proved most consistent with the findings of randomized studies.

Can calcium help?
A recent Dartmouth study in the Journal of the National Cancer Institute showed that calcium may provide some protective effect against colorectal cancer. John Baron, M.D., and colleagues examined data from an earlier trial that had randomly assigned 930 patients with a recent adenoma to take either a placebo or a 1200-mg calcium supplement. Adenomas are benign tumors that may progress to colorectal cancer. The new analysis, of 822 records, found that in the first five years after patients' treatment ended, the risk of another adenoma was 31.5% in the calcium group and 43.2% in the placebo group. The protective effect was not evident after five years, however.

Cellular call
Ethan Dmitrovsky, M.D., led a team that identified a new way in which arsenite, a form of arsenic, acts against a rare cancer called acute promyelocytic leukemia (APL). The study, published in the Journal of the National Cancer Institute, showed that arsenite causes rapid destabilization of lysosomes, a part of the cell containing enzymes that are able to destroy APL cells; when the lysosomes break apart, the enzymes are released. It had previously been known that arsenite was effective against APL, but the reason was poorly understood.

A trial to see if a tuberculosis vaccine keeps HIV-positive Tanzanians from getting TB found that 94% of the subjects showed an immune response; DMS was a partner in the study.

Using digital 3D modeling, radiology researchers found erectile dysfunction may be affected by bike-riding, due to arterial constriction. Rider position and seat design are the key factors.

DHMC was recently reverified as a Level I trauma center by the American College of Surgeons. It's one of only 45 centers nationwide with level I "adult and pediatric" designation.

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