The number of independent medical reviews used to resolve California workers compensation medical disputes rose 4.4% in the first half of 2018, compared with the first half of 2017, and more than 90% of the disputed cases are upheld in the process, according to a report released Monday by the California Workers’ Compensation Institute.

The Oakland-based institute reported that 89,843 independent medical review decision letters were issued in the first half of 2018 in response to applications submitted to the state after a utilization review physician modified or denied a medical service request. Independent doctors upheld 90.7% of the utilization review physician’s modification or denial. In 2017, that figure stood at 91.2%, according to the report.

California law requires that workers compensation claims administrators have a utilization review program to ensure care is supported by clinical evidence outlined in medical guidelines adopted by the state. Most treatment requests are approved by utilization review, but in 2012 state lawmakers adopted independent medical reviews to give injured workers a chance for an independent medical opinion on treatment requests that utilization review physicians deny or modify.

Prescription drug requests represented nearly half of this year’s independent medical review decisions, with opioids accounting for 32.3% of the 2018 prescription drug independent medical reviews — up from 29.7% in 2017, the institute reported.

The increase follows the adoption of new opioid and pain management guidelines in late 2017 and implementation of the workers drug comp formulary that took effect Jan. 1.

Requests for physical therapy, injections, durable medical equipment, diagnostic imaging and surgery accounted for a third of the 2018 independent medical reviews, but no other medical service category accounted for more than 3.5% of the disputed requests, the institute reported. The 2018 uphold rates for the various service categories range from 77.8% for psychology services to 93% for acupuncture, according to the report.

The latest data found that a small number of physicians continue to account for most of the disputed medical services that go through independent medical review, according to the findings, which were in line with last year’s figures. The top 10% of physicians identified in the independent medical review decision letters issued in the first half of this year — 1,190 doctors — accounted for 86% of the disputed service requests during that period. The top 1% — 119 providers — accounted for 44% of the disputed services, according to the report.