OHTA shows tepid support for PETin technology assessment study

HCFA granted Medicare reimbursement anyway

The Office of Health Technology Assessment displayed lukewarmenthusiasm for cardiac PET imaging using rubidium-82 in a studythat formed the basis for Medicare reimbursement of the procedure,which began last March. The study states that rubidium PET maybe no more specific or sensitive than thallium SPECT in assessingmyocardial ischemia. The conclusion is surprising in light ofthe decision by the Health Care Financing Administration to reimbursefor rubidium-82 studies (SCAN 4/12/95).

"Despite this evaluation, HCFA decided to go ahead andapprove it,"said Dr. Steven Larson, president of the Institutefor Clinical PET and chief of nuclear medicine services at MemorialSloan-Kettering Cancer Center in New York City.

The public release of the report, which was submitted to HCFAmore than a year ago, provides a less-than-flattering window intothe decision-making process at the agency, which manages the Medicareprogram. In this case, HCFA required the generation of a technicalreport before it would grant Medicare reimbursement, then heldoff on a decision for nine months after the report was submitted(SCAN 9/14/94). In the end, the agency put little stock in thereport's conclusions.

Even so, this case study of the decision making that surroundedthe rubidium-82 issue is encouraging. Larson suggests that HCFAattempts to look at various sides of the issue and in the endemphasizes the judgment of individual physicians more than anysingle technical report.

"I think (OHTA) is trying to do its job and does the bestit can," Larson said. "But it is confining itself strictlyto the literature. There is additional information available fordecisions, such as the one HCFA made, that I think bears on thispoint."

In its report, OHTA concluded that while both SPECT thalliumand rubidium-82 PET appear to be useful for evaluating myocardialischemia and for making further management and therapeutic decisionsregarding cardiac patients, there was insufficient evidence inthe peer-reviewed literature to determine whether one method wasany more specific or sensitive than the other.

The reason is that published data about sensitivity and specificitywere inconsistent, according the author of the report, Dr. StevenHotta, a pediatrician with a Ph.D. in biochemistry.

"You can get a preference for one or the other,"Hotta said. "What I was trying to show was that there isa tremendous amount of overlap."

Hotta compiled a table of nine studies with thallium SPECTsensitivity ranging from 76% to 95% and specificity ranging from44% to 94%. Rubidium PET sensitivity ranged from 76% to 95% andspecificity from 86% to 100%.

On the positive side, OHTA concluded that the image of cardiacperfusion produced with rubidium is clearer than SPECT imagesmade using thallium, due to the higher pixel counts and correctionsfor attenuation possible with PET as opposed to SPECT. It wasnot clear, however, whether the improved images had any diagnosticsignificance.

In the end, Hotta concluded that "All three methods --planar thallium scintigraphy, thallium SPECT and rubidium PET-- may be used to evaluate myocardial perfusion noninvasivelyin most patients who are referred to a cardiac center."

Hotta was, however, able to compare the costs of cardiac diagnostics.Planar thallium scintigraphy cost $700 to $900; thallium SPECT,$1100 to $1400; and rubidium PET $1000 to $2800. The differencein costs apparently was factored into HCFA's decision regardingthe reimbursement rate for rubidium PET, which itself has beensomewhat controversial due to PET's higher cost.

"If you look at the reimbursement policy that HCFA hasput forth, the cost (for rubidium PET) to the system (federalgovernment) is equivalent to SPECT," Hotta said.

In today's health-care environment, cost concerns are inescapable.And release of the report to the general public and physiciancommunity brings into question the credibility of rubidium-82PET at a time when referring physicians are sensitive to the needto be conservative in their diagnostic prescription. But the ICP'sLarson is not concerned.

"Over time the diagnostic tests that last are the onesthat are most cost-effective," Larson said. "Many timesthallium will be used; in other instances rubidium will answerthe question better. Physicians are in the best situation to makethis sort of judgment."