Every year, thousands of Americans in what should be the prime of life die from a dozen illnesses that can be treated or prevented by routine medical care, a study by District health officials shows.

The victims of these needless deaths are much more likely to be black than white, the study found. Blacks had higher death rates than whites for 11 of the 12 illnesses, and the overall black mortality rate was 4.5 times the white rate.

The study is important, researchers said, because it shows that lack of access to basic care not only worsens illness and increases hospital spending but also can be lethal.

"People should not be dying of these diseases in these age groups," said Eugene Schwartz, chief of the bureau of cancer control in the District Commission of Public Health and a co-author of the study.

The 12 medical conditions the study looked at are appendicitis, influenza, asthma, gallbladder infection, pneumonia and bronchitis, Hodgkin's disease, cervical cancer, hypertensive heart disease, tuberculosis, abdominal hernia, acute respiratory disease and rheumatic heart disease. They are called "sentinels" because they are rarely fatal in people ages 15 to 64 if treated promptly. Deaths from such diseases are a sign of gaps in health care.

"People are dying from 12 medical conditions that can be cured or treated if {the patients} only had access to basic medical care that a family physician can provide," said Marc Rivo, a co-author and deputy administrator of the the District public health commission. "We're not talking about new drugs or new technology or sophisticated care in a major medical center."

Nearly 122,000 Americans died of those conditions between 1980 and 1986, the study found. More than 80 percent of them were black, even though only 12 percent of the population is black.

The biggest killer among the 12 treatable conditions studied was hypertensive heart disease -- damage to the heart and arteries caused by abnormally high blood pressure -- followed by pneumonia and bronchitis, cervical cancer and asthma.

Most of those deaths were preventable. Risk of hypertensive heart disease is dramatically reduced when blood pressure is kept under control. Similarly, if pneumonia and bronchitis are promptly diagnosed and treated, they are rarely fatal in this age group unless related to AIDS. With early detection by a Pap test, cervical cancer is much less likely to be fatal.

The study was conducted by four officials from the District health commission: Reed V. Tuckson, who resigned as health commissioner last year to become senior vice president of the national March of Dimes Birth Defects Foundation; Vincent Y. Kofie, an epidemiologist with the cancer bureau; Schwartz and Rivo. Findings were reported in the September issue of the International Journal of Epidemiology.

While the study cannot specify why so many people died of these treatable illnesses, poverty and lack of health insurance are seen as prime suspects because they keep patients from getting basic care. Uninsured patients are more likely than insured patients to die in the hospital from the same disease, a national study led by researchers at Georgetown University School of Medicine reported this month.

"It is said that we have the best health care system in the world," Schwartz said. "Maybe it's more correct to say we have the best health care money can buy."

A study sponsored by the D.C. Hospital Association in 1988 found that about one third of the uninsured patients admitted to District hospitals had medical conditions that could have been treated or prevented with timely care in a clinic or doctor's office. The new study takes those findings one step further, said Rivo, who is president of the District of Columbia Academy of Family Physicians.

"Not only are patients getting admitted to the hospital unnecessarily," he said, "but they are dying."

While blacks are four times more likely to rely on emergency rooms and hospital clinics for health care, low-income people of all ethnic groups "must postpone seeking primary care until their need for treatment becomes urgent and . . . then turn to hospital emergency rooms," the study concluded.

"It's not that you're black, it's that you don't have health insurance," Rivo said. "It's not that you're black, it's that you're poor." Sorting out exactly why people don't get the health care they need is complicated, the study noted. Designing solutions is even more so. But they begin with what doctors call primary care -- a doctor's office or clinic where patients can go on a regular basis for checkups, routine care and follow-ups.

The entire health care system tends to give short shrift to primary care, Rivo said. Medical schools train more specialists than family physicians. Health insurance policies are more likely to pay in full for elective surgery than routine physicals, cancer detection, counseling of patients who smoke or drugs for controlling blood pressure.

Family physicians, as a group, are the lowest paid among medical specialties, according to the American Medical Association. The average doctor's income reached $155,000 in 1989. Surgeons were the highest paid specialists, averaging $221,000, and family physicians the lowest, at $96,000.

More than 30 million Americans -- including an estimated 110,000 District residents -- have no health insurance at all. The public clinics on which these people rely are underfunded, poorly staffed and rarely open during off-hours when the working poor can visit them. "The system for low-income people discourages them from using primary care," Rivo said. "The poor delay seeking care until it's absolutely necessary, and then they seek it in hospital emergency rooms when it's often too late."

Broadening health insurance coverage is a key first step but not enough by itself, he said. A comprehensive approach to boosting primary care would include educating the public about preventable health problems, extending clinic hours and improving public transportation.

For many poor residents of the District, Rivo said, "it's a bus ride or two to the clinic. And when they get there, the pharmacy may be closed."

When budget cuts necessitated closing the District's Congress Heights health clinic during the evening, physicians at the District Commission on Public Health pitched in to staff it voluntarily on Wednesday nights.

Tuckson recalled a 40-year-old woman who showed up one evening at the clinic with dangerously high blood pressure. She was out of medication and said she couldn't afford to buy more. She worked at a marginal job with no health insurance and had young children at home.

"Let's say we weren't open," Tuckson said. "She'd walk around for maybe another year and get really sick with congestive heart failure and she'd go to the emergency room and sit there till midnight and they'd have no choice but to admit her even though she had no insurance.

"That lady is classic," Tuckson remembered. Unless she gets basic care, she has "shortened her life." Nor is she the only victim. "What we don't see {right away} is that she's not feeling well all this time and she's not taking good care of those kids," Tuckson said.

Rebuilding the health care system involves two monumental efforts, Tuckson said. The first begins with an attitude, one that tells a patient: "You are important. Your life has value. Don't disrespect it. "Second, you give people access to care -- the full range of health services to help them act in their own best self-interest." That means health insurance, primary care, transportation, clinics in the neighborhoods where people live and open during hours when they aren't at work.

"What else in the world is more important than this?" Tuckson said. "What other thing on the public agenda matters more than whether the citizenry survives?".

A recent study looked at death rates from 12 conditions that are largely preventable or easily controlled when patients have access to prompt and regular medical care. In both the District and the nation as a whole, blacks were more likely than whites to die of most of those illnesses.

The following table shows how black death rates compare with those of whites:

.............................In the U.S..........In the District

Tuberculosis................ 8.9 times higher... 23 times higher

Cervical Cancer............. 2.6 times higher... 3.5 times higher

Hodgkin's disease........... 20 percent lower... 70 percent lower

Rheumatic heart disease..... 2.8 times higher... *

Hypertensive heart disease.. 6.5 times higher... 3.4 times higher

Acute respiratory disease... 2 times higher..... *

Pneumonia and bronchitis.... 3.8 times higher... 3.5 times higher

Influenza................... 1.3 times higher... *

Asthma...................... 4.4 times higher... 2.7 times higher

Appendicitis................ 3.2 times higher... 1.04 times higher

Hernias..................... 2.4 times higher... 3 times higher

Gall bladder infection...... 1.6 times higher... *

* (For these conditions, there were no reported deaths among whites in the District)