Many Patients With Hyperparathyroidism Going Undiagnosed

By Linda Carroll

July 30, 2020

(Reuters Health) - Many patients who have hyperparathyroidism may be missed because physicians aren't testing for it even when two indications for screening - a kidney stone and hypercalcemia - are present, a U.S. study suggests.

An analysis of data from more than 7,500 veterans who had kidney stones and hypercalcemia revealed that fewer than 25% had their serum PTH level tested, according to the report published in JAMA Surgery.

"As clinicians, we can do a better job screening patients with kidney stones and high calcium for hyperparathyroidism," said the study's lead author Dr. Calyani Ganesan, a clinical instructor in the division of nephrology at the Stanford University School of Medicine in California. "I think this is due to a combination of a lack of awareness and the fact that there are so many other chronic diseases that people are dealing with that they put this on the back burner."

Making matters worse, among patients who were diagnosed with hyperparathyroidism, just 26% had surgery to correct the condition in the following two years. It's possible, Dr. Ganesan said, that doctors are concerned that the surgery might be risky in these patients, many of whom are older and have multiple comorbidities. "But we know this surgery is very successful and it has a low rate of complications," she said.

To take a closer look at screening rates for higher-risk patients, Dr. Ganesan and her colleagues turned to data from the Veterans Health Administration collected between January 1, 2006 and December 31, 2014. The researchers first identified patients with kidney stones and a serum calcium measurement six months before or six months after their index stone diagnosis. Measured hypercalcemia was defined as a serum calcium concentration greater than 10.5 mg/dL.

After excluding patients who had previously been screened for hyperparathyroidism, there were 7,561 patients fitting the researchers' criteria. Most of the patients, 94.4%, were men. Among the 7,561 patients, 1,873, or 24.8%, completed a serum PTH level measurement around the time of their initial stone diagnosis.

The factor that most strongly affected the chances that a patient would be tested for hyperparathyroidism was whether the individual saw a specialist. Patients were more likely to be tested if they saw either a nephrologist or urologist (odds ratio 1.56) or both (OR 6.57), compared with those who didn’t visit stone specialty clinics, and the odds were nearly five-fold higher when patients saw an endocrinologist (OR 4.93), the study team notes.

Among the 717 patients with biochemical evidence of hyperparathyroidism, 189, or 26.4%, underwent a parathyroidectomy within two years of a stone diagnosis.

Part of the problem may be that physicians don't realize that a kidney stone can be the sign of a systemic disease that can lead to other problems, such as osteoporosis, Dr. Ganesan said.

The new findings underscore the fact that hyperparathyroidism is an underdiagnosed condition, said Dr. Michelle Semins, an assistant professor at the University of Pittsburgh School of Medicine and director of the UPMC Kidney Stone Center.

Not only is it important to diagnose hyperparathyroidism to prevent future stones, but also to prevent damage to other parts of the body, including the bones, the heart and the brain, Dr. Semins said.

It's also quite likely that the problem is even worse than the findings suggest, Dr. Semins said. "As the authors mention in their limitations, in this study they only considered patients with elevated PTH to have the condition, but patients can still have the diagnosis with normal but inappropriately high normal PTH levels," she said. "This means underdiagnosis of these patients is even worse than suggested here."

It's good that studies like the present one are drawing attention to this problem, said Dr. Ketan Badani, vice chair of urology and director of the Comprehensive Kidney Cancer Program at the Mount Sinai Health System in New York.

One reason that doctors may not be referring patients for parathyroid testing could be that they look at the kidney stone as an acute problem, Dr. Badani said. "Most are dealing with the immediate problem of the stone itself," he said. "If I look at practice patterns across the field, by and large, people with kidney stones are not getting metabolic evaluations."

Just realizing that the condition is underdiagnosed might make physicians more attuned to it, Dr. Badani said.

SOURCE: https://bit.ly/39HWtQj and https://bit.ly/3ffnXho JAMA Surgery, online July 29, 2020.

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