Blog posts tend to be breezy, but they should still be rooted in the facts. This post took too much liberty with the findings from a recent study on bone density screening and left readers with the impression that regular screenings don’t offer much benefit. There is a case to be made for this impression, but the story does not make it. Compounding the problem is a significant factual error at the top of the story. The U.S. Preventive Screening Task Force does not recommend screening every two years. It recommends "routine screening" without specifying the interval for testing: a wise choice in the absence of much data. The task force simply cautions that testing more frequently than every two years is not supported by data: "No studies have evaluated the optimal intervals for repeated screening. Because of limitations in the precision of testing, a minimum of 2 years may be needed to reliably measure a change in bone mineral density; however, longer intervals may be adequate for repeated screening to identify new cases of osteoporosis."
The U.S. Preventive Services Task Force reports that "half of all postmenopausal women will have an osteoporosis-related fracture during their lives, including one-quarter who will develop a vertebral deformity and 15 percent who will suffer a hip fracture. Hip fractures are associated with high mortality rates and loss of independence." This study is important because it addresses the issue of screening intervals for a test that is already widely used in older women and likely to be used more widely as our population ages. Until now the decision about how often to screen has been guided more by the availability of insurance coverage than by sound clinical evidence.
The story presents the findings as a liberation, of sorts. It says, “women 67 and older with normal bone-mineral-density scores may not need to be screened for another 10 years — a finding that could release thousands of women from the costs and inconvenience of repeated bone-mineral scans over the course of several decades.” What are those costs? The story never says. The U.S. Preventive Services Task Force says, “Costs of screening vary with technique, and average 2000 Medicare reimbursement rates were $133 for DXA and $34 for ultrasonography. … Treatment costs also vary; alendronate currently costs approximately $3 per daily dose."
No benefits were quantified in this story.
There no harms mentioned in this story. Potential harms would include missed or delayed diagnosis of osteoporosis, resulting in increased risk of harm from fracture that might have been prevented with earlier detection and treatment. The aforementioned U.S. Preventive Services Task Force mentions a number of potential harms from too much screening, including “anxiety and perceived vulnerability that may be unwarranted.” Also, “Some women may be falsely reassured if abnormal results from last year’s DXA appear "improved" on this year’s normal calcaneal ultrasonogram. The potential time, effort, expense, and radiation exposure of repeated scans over a lifetime have not yet been determined.” It goes on to say, “Potential harms may also arise from inaccuracies and misinterpretations of bone density tests. The variation among techniques, along with the lack of methods to integrate bone density results with clinical predictors, makes it difficult for clinicians to provide accurate information to patients about test results. In one study, physicians found densitometry reports confusing, and were not confident that their interpretations of T-scores were accurate. False-positive results could lead to inappropriate treatment, and false-negative results could lead to missed treatment opportunities.”
The story describes the nature of the study, the size of the cohort, how long it lasted and a few other facts. It does not make an attempt to evaluate the quality of the evidence. One of the biggest flaws in this story has more to do with the framing than with the study’s findings. The story flippantly says that “The U.S. Preventive Services Task Force recommends bone-density testing every two years. But that’s just a guess. No one really knows how often screenings should occur.” A guess? How insulting to the medical experts who put together a “Summary of the Evidence” for the task force. Unfortunately, fewer people will read this summary over the next few days than will read the Times story.
Neither story reviewed on this topic engaged in disease mongering.
There are no outside experts quoted in this story, and the only reference to an outside organization, the one to the U.S. Preventive Services Task Force, is used dismissively.
It is clear that the alternative to less frequent screening is conventional frequency of screening, i.e. every two years.
Availability is at least implied by the statement that the news would release "thousands of women" from costs and inconvenience of testing. But the story could have been far more explicit about how widespread such screening has become. Nonetheless, we’ll give it the benefit of the doubt.
The story does establish the novelty of less frequent bone density screening.
The only quote in the story comes directly from a news release. This is an unfortunate trend that we’ve seen far too often.