*Updated May 13, 2014, with full list of low-value procedures evaluated in the study.

Medicare may have spent as much as $8.5 billion on procedures and tests that likely provided "minimal or no benefit" to patients’ health, and medical devices are high on the list of culprits, according to a new study from Harvard Medical School.

Researchers examined Medicare spending for 26 procedures deemed "low value," ranging from imaging for back pain to knee arthroscopy for arthritis and MRI for headaches (full list below), concluding that at least 1 in 4 Medicare recipients received at least 1 such procedure in 2009.

The authors examined 6 categories for suspect care: cancer screening, diagnostic and preventive testing, preoperative testing, imaging, cardiovascular testing and procedures and other surgical procedures.

The authors counted nearly 22 million instances of Medicare reimbursement for supposedly ineffective procedures in each category, affecting 42% of care recipients. They pared down their findings in an attempt to tease out just the procedures that were least likely to be effective, weeding out emergency room cases and other indicators of necessary care. The researchers settled on 9.1 million instances of low-value care, affecting about 25% of recipients.

Some of the suspect procedures are considered beneficial only in rare instances or in high-risk patients, the authors noted. If a significant portion of the tallied low-value procedures were conducted in those rare patients, Medicare waste would still amount to $1.9 billion.

The final tally comprises "modest proportions of overall spending but affected substantial proportions of beneficiaries and may be reflective of overuse more broadly," the authors wrote.

Even the costs are coming directly out of patients’ pockets, they may be paying with recovery times, pain or other side effects of unnecessary care.

The data was gathered from Medicare spending reports from 2009, but the authors warned that wasteful spending has likely only increased since then. Furthermore, the 26 examined procedures are "just the tip of the iceberg," lead author J. Michael McWilliams told the Harvard Medical press.

"There are hundreds of other low-value services," he said.

Nationwide campaigns have sought to curb needless care, but it’s not clear yet whether they’ve been effective. The ‘Choosing Wisely’ initiative, which aggregates specialty-specific lists of potentially unnecessary services, was launched in 2012.

*The full list of low-value procedures tallied in this study included:

• Arthroscopic surgery for knee osteoarthritis
• Back imaging for patients with non-specific low back pain
• Percutaneous coronary intervention with balloon angioplasty or stent placement for stable coronary disease
• Renal artery angioplasty or stenting
• Electroencephalogram for headaches
• Preoperative echocardiography
• Preoperative chest radiography
• Cancer screening for patients with chronic kidney disease (CKD) receiving dialysis
• Cervical cancer screening for women over age 65
• Colorectal cancer screening for adults older than age 85 years
• Prostate-specific antigen (PSA) testing for men over age 75
• Computed tomography (CT) of the sinuses for uncomplicated acute rhinosinusitis
• Head imaging in the evaluation of syncope
• Head imaging for uncomplicated headache
• Screening for carotid artery disease in asymptomatic adults
• Screening for carotid artery disease for syncope
• Stress testing for stable coronary disease
• Carotid endarterectomy in asymptomatic patients
• Inferior vena cava filters for the prevention of pulmonary embolism
• Vertebroplasty or kyphoplasty for osteoporotic vertebral fractures
• Preoperative pulmonary function testing (PFT)
• Bone mineral density testing at frequent intervals
• Homocysteine testing for cardiovascular disease
• Hypercoagulability testing for patients with deep vein thrombosis
• Parathyroid hormone (PTH) measurement for patients with stage 1-3 CKD
• Preoperative stress testing