Q. What is Medicare Part D?

A. Congress approved the Medicare Modernization Act in 2003 to provide affordable prescription drugs to seniors and the disabled. It took effect in 2006. Some 36 million people are now enrolled in private insurance plans that pay most of the cost of their drugs. Medicare spent $62 billion subsidizing the program last year.

Q. Where does this data come from?

A. When pharmacies dispense prescriptions to Medicare patients, they transmit information to Part D plans about the patient, the prescriber, the drug, its strength and retail cost. The plans pay the claims and then submit the data to the Centers for Medicare and Medicaid Services, which oversees Medicare. ProPublica obtained and analyzed data for 2007-2011 for this project. We are currently displaying data for 2011 — covering more than 1.1 billion prescriptions and refills. (We had previously displayed data for 2010; that information is no longer available.)

Q. Why is my health provider not in here?

A.  Medications administered to Medicare enrollees during an office visit or in a hospital are covered by another part of Medicare, not Part D. That means they will not show up in our data. In addition, providers who did not write at least 50 prescriptions (including refills) of at least one drug under Medicare Part D will not show up. Nearly 364,000 providers are reported on Prescriber Checkup.

Q. How do you know a provider’s specialty?

A. We used the primary specialty chosen by the health professionals themselves. Providers are required to identify this specialty when they apply for a federal health care ID number. (In cases where we did not have a prescriber’s ID number, or if a specialty is not specified, no comparisons are shown in Prescriber Checkup.) A provider’s chosen specialty doesn’t always mean the person has special training or certification. For example, some doctors select a specialty called “Specialist,” which can be a catchall for providers of different fields.

Be aware that doctors may have incorrectly entered their specialty or may have changed specialties without updating their profiles. Some classified themselves as a group practice; we identified this in parentheses next to the specialty. The date each provider updated his or her profile is noted.

Q. What does it mean if my doctor has longer or shorter average prescription lengths?

A. When a provider writes a prescription, he or she specifies how many days the patient should take it. We looked at the average length of prescriptions for every drug and every provider and compared it to peers in the state. In some cases, for example, a provider may write shorter prescriptions while adjusting a patient’s medication. That could make the provider’s prescription count appear higher than peers. On the other end, if providers write prescriptions for more days than average, they may have fewer prescriptions.

Q. What about the cost of drugs?

A. Each prescriber’s profile page notes the total retail price of their drugs and the average price per prescription. These prices include patients’ copayments and the amount reimbursed by Part D insurance plans. But the costs do not reflect confidential rebates that drug companies negotiate with insurers. As such, the listed price is likely to be higher than the final price paid. A report from the inspector general of the Department of Health and Human Services calculated overall manufacturer rebates of 19 percent for the 100 name-brand drugs that Part D spent the most money on in 2009.

Q. Why do you display the percentage of a provider’s claims that are covered by the low-income subsidy?

A. The low-income subsidy has been an integral component of Part D from the start. The government picks up the vast majority of drug costs for the poor, making a generic drug no more than $2.65 and a name brand no more than $6.60. As a result, poor patients and their doctors have little financial incentive to choose a generic over costlier name brands.

Q. Why is a provider’s percentage of name-brand drugs relevant?

A. About three-quarters of drugs of drugs dispensed in Medicare are generics. When doctors choose more name brands, their costs are typically higher. Generics often work the same as name brands and have the same active ingredient. Although some medications do not have exact generic versions, there usually is a similar one in the same category. A doctor’s percentage of brand-name drugs may be a gauge of how cost effective that doctor’s prescribing is. Specialists who treat some conditions, such as HIV/AIDS, use more brand-name drugs because there are few available generics to treat them. Also, a small number of hospitals and health centers serve as safety net providers for the poor and receive rebates from pharmaceutical companies for name-brand drugs they prescribe, under a federal program distinct from Medicare. (It does not apply to physicians in private practice.)

Q. What does the bar graph in the “Another View” section of a provider’s page mean?

A. Prescriber Checkup features a chart comparing prescribers to others in their state and specialty. It clusters prescribers based on their drug preferences and volume. On the chart, a provider who appears far to the right has drug preferences and volume that markedly differ from others.

Q. What’s not included in this data?

A. Prescriber Checkup doesn’t cover Medicare enrollees who receive drug coverage from current or former employers, the U.S. Department of Veterans Affairs or some retiree health plans. Part D does not include drugs dispensed in a hospital, hospice or during some short rehabilitation stays in a skilled nursing facility. It also does not include medications administered in a doctor’s office, such as intravenous cancer drugs. These are covered by other parts of Medicare.