IT IS EASY to conclude that most medical patients are masochists. Consider the 45-year-old employe of a Cadillac dealership who went to his doctor for a check-up. His only complaint was that every so often, over the past few years, he had "gas pains" in his chest at night -- particularly after heavy holiday meals. The doctor could find nothing wrong; even the electrocardiogram was normal. But the man was not convinced; he insisted on having more tests, all of which revealed no hint of any illness.

Finally, his doctor sent him to a cardiologist who performed a vectorcardiogram test (a variation on the standard ECG) andconcluded that the man must have experienced a "silent" heart attack years ago that put him at risk for a far more serious attack at any moment. The cardiologist dictated a total change of life-style. The man was ordered to sell his two-story home and move into a residence without stairs to climb, to abandon his ethnic diet for one abhorrent to his tastes, and to give up his business because of the emotional stress involved. Surprisingly, the man complied with this bitter prescription -- solely on the basis of one vectorcardiogram and the doctor's belief in that test, even though it is generally considered to be only 50-percent accurate.

This case is not only true. It is typical.

If patients aren't masochistic, why else would they demand every possible medical test -- at the rate of 33 million a day in the U.S. -- with such fanatic zeal? What perverse pleasure can be derived from being stabbed by needles, exposed to X-rays, connected to Frankenstein-like machines or having one or more very private orifices invaded and explored? Or is there an unconscious wanton desire for the titillation of participating in dangerous procedures? For, truth be told, every medical test encompasses some degree of risk; and in some cases, the hazards far outweigh the perils of the disease.

Moreover, according to the Center for Disease Control, one out of every seven test results reported back to doctors from laboratories is either in error or unreliable. To clinical pathologists, any test less than 95-percent accurate is appraised as poor. Yet the majority of medical tests are no more than 80 percent accurate.

Nonetheless, an American Medical Association report published last year stated that over 80 percent of all doctors admit that they order many more medical tests than are really necessary -- primarily for their profit and legal protection. As a result, half of all health-care costs go for medical tests: $225 billion in 1985. But if government and insurance reimbursement were limited to tests with an accuracy rating of 80 percent or better, medical care costs might be reduced by more than $50 billion.

Blue Cross and Blue Shield have already started in that direction. Last April the Blues announced their "Guidelines on Diagnostic Testing," which added to their already profuse list of outmoded tests 53 more laboratory tests -- along with routine (non-specific) use of the chest X-ray and ECG -- as generally inappropriate. Translated, this means they will no longer reimburse doctor or patient for the test unless it can be justified as absolutely necessary in diagnosis and treatment. The "Guidelines" for just these few of the more than 2,000 different medical tests in regular use are intended to save Blue Cross and Blue Shield at least $18 billion a year.

Of course medical tests, in their proper place, can be worthwhile in helping a doctor solve a diagnostic dilemma. But better than any test is a doctor who takes an elaborate history of your illness and who will listen. It is an accepted medical maxim that 70 percent of every diagnosis comes from what the patient tells the doctor; 20 percent from the physical exam; and only 10 percent from tests. Of course, you must be as honest as you are thorough in describing your complaint, including possibly remotely related facts even if somewhat embarrassing. If your doctor will not listen, you stand to lose a great deal -- not just from the dangers of the tests that are substituted for circumspection -- but from the fact you are being treated as a specimen instead of a person. If your doctor is a listener, you already have a 70 percent headstart toward the goal of a cure.

Why, then, do patients persist in requesting so many procedures? For one thing, they no longer trust their doctors as they once did. A Harris survey taken 20 years ago found that 73 percent of patients said they had a great deal of confidence in their doctors. When the poll was repeated in 1985, the figure had dropped to only 32 percent. For another, patients may enjoy the feeling of importance that accompanies medical testing.

Whatever the reason, they rarely know what they are getting into -- and what might be getting into them -- when exposed to an area of medicine that is not even subject to the same rules and regulations applied to drugs, automobile tires and tennis balls. Unlike medicines, medical tests do not have to prove themselves accurate, safe or even worthwhile to be ordered or performed by your doctor. There are no government laws or professional standards that apply to medical testing. Any doctor can order or perform any medical test regardless of whether or not it has any value and notwithstanding all known risks.

To be sure, some of the devices used in medical testing are reviewed by the FDA. An X-ray machine must work properly and not give off extraneous radiation; an ECG machine must not be capable of causing an electrical shock; even a thermometer must be accurate at the time of manufacture. But that is as far as it goes; in most states, no one reviews the capability, technical ability or experience of the person who ultimately operates the test device. It is rare, in fact, that an X-ray technician is subject to a licensing procedure that requires proof of proficiency. No agency protects you from a careless overdose of radiation or an improperly taken X-ray, the results of which could fail to show some hidden pathology or, even worse, wrongly suggest some dire diagnosis.

But even if correctly administered, the test itself may be both inconclusive and dangerous. For example, the accuracy rate of gallbladder X-rays, where the patient swallows contrast chemicals to help make the gallbladder more visible, is reported in several journals, including the radiologist's own official publication The American Journal of Roentgenology, to be only from 13 to no more than 30 percent accurate. Even if the dye is injected, the rate is no better than 50 percent. Yet according to a report in American Family Physician, from 200 to 800 people die every year as a consequence of reactions to such dyes. Other ostensibly less risky side-effects of the dyes include kidney failure, mental aberration and chromosome damage.

Or take the familiar stress electrocardiogram, in which your ECG is taken while you are on a treadmill, stationary bicycle or walking. The most recent report in Occupational Health & Safety calls it 16 to 21 percent accurate when attempting to reveal hidden heart trouble in asymptomatic individuals and even less accurate when it comes to predicting future heart disease. Were that not bad enough, the stress ECG is known to signify heart trouble in at least 50 percent of people who are ultimately shown to have no heart disease at all. Even the standard ECG, taken while you are lying down, is considered only 75 percent accurate as a screening device. Worse yet, for every 10,000 times the stress test is performed, at least four people have a heart attack while being tested and one of those four dies.

As for blood tests, almost all of them can indicate a hundred or more different conditions when they show a positive result. A blood test almost never specifies any one illness. Worse, the accuracy of most blood tests can be affected by physical activity, diet, stress, medication and even your body's position. Or the lab can let your blood sample sit around for hours before testing, use reagents that are out of date, take blood from your arm while the tourniquet is still in place, operate the testing machine incorrectly or mislabel your specimen.

On the risk side, there is hematoma (blood leaking from the vein where the needle punctured it), broken needles requiring surgical removal, and the possibility of acquiring an infection such as AIDS or hepatitis from needles or syringes that have been used before -- despite their having been sterilized. More recently, brand-new, never used, supposedly sterilized blood collecting devices were found to be contaminated and the source of a transmitted infection.

One of the most common blood tests used to diagnose a heart attack, called creatine phosphokinase, can show a false positive result in a healthy individual simply because he did nothing more than exercise moderately a few days earlier. It has happened that a stomach upset in a fitness buff was treated as a coronary thrombosis because all the extraneous but relevant information concerning that test was not taken into consideration.

Yet millions of such dubious procedures are performed daily -- at considerable profit to doctors, who are inundated with direct-mail advertisements and salespersons stressing the money to be made from testing. There are desk-top machines which will perform a dozen blood tests at at total cost to the operator of less than $1. The doctor can then charge anywhere from $5 to $25 for each test. One manufacturer promises an extra income of $44,000 a year by performing only 30 tests a day. The initial cost of that machine is $1,000.

Once, doctors used to "test" the circulation of your lower legs by putting a hand on each of your feet. If there was a slightly blocked artery or vein, a difference in temperature was obvious. Today, doctors are more apt to use a device that detects skin color changes in your lower legs. Virtually the same diagnostic information is obtained either way. But the doctor receives no payment for laying on hands, whereas he can collect up to $250 from Medicare and other insurers for the few minutes it takes to touch the color-detection pad to your skin. The company that markets this instrument makes no hesitation in telling doctors that if they only test one patient a day with their device, the profits will be a minimum of $3,900 a month.

It is estimated that more than 50 percent of all medical tests are now being performed in physician's offices; that is over 7 billion a year. Ten years ago, no more than 10 percent of such tests were done in an office setting and less than 10 percent of all doctors maintained their own labs. Today 90 percent do. Could this be because three years ago government health plans stopped reimbursing doctors for tests performed in commercial laboratories? Prior to that time, doctors were allowed to charge any additional fee they wished over and above what the lab charged them. Then, starting in 1985, hospital payments for Medicare patients no longer included unlimited fees for medical tests; but Medicare will still pay the doctor for the same tests if performed in the office. So will many private insurance plans, often without question as to accuracy or need.

But questions are very much in order. The CDC, which reviews the accuracy of medical tests throughout the country, has revealed that more than one-third of office testing is performed by employes with no formal laboratory training. Labs in doctors' offices are, with very few exceptions, not required to be inspected or licensed as are commercial establishments and hospitals. In 37 of the 50 states, office laboratories are totally exempt from any proficiency regulations; and in nearly all instances they are even exempt from the quality-control requirements usually demanded by Medicare regulations.

If a test is accurate, appropriate and necessary, there certainly should be no geographic basis for its application. Yet, in a recent Rand Corporation study of the types and frequencies of certain tests performed in 13 different U.S. communities containing similar numbers of Medicare patients, there were four and a half times as many X-rays of the gallbladder performed in one city as in another with a similar number of radiologists. Three and a half times as many patients underwent a stress ECG in one city as did those in a comparable area.

A 1984 study published in the Journal of the American Medical Association compared American and British doctors' treatment of patients with high blood pressure. Boston physicians performed up to 40 times as many tests during a two-week period as did their London colleagues. The most commonly exploited was the ECG; Americans performed this test several times on each patient despite the fact that no relevant data were obtained. Eight times as many X-rays were taken by the American doctors, most of them of parts of the body essentially unrelated to high blood pressure; not one of those was ordered by a British doctor. The major reason for the difference in the amount of testing turned out to be the fee-for-service system in America; British doctors receive no reimbursement for either ordering or performing medical tests. Of particular interest, no difference was detected in the quality of the care provided by either group. The study concluded that American patients seem to prefer testing, regardless of its need or effect.

But to give doctors their due, there is another factor involved: "defensive medicine." That is, the excessive performance of tests to protect against the possibility of losing a malpractice suit. Last year, the AMA told Congress that this form of superfluous testing raises the cost of medical care nationwide by an estimated $40 billion a year. Doctors, of course, blame lawyers and our litigious society. Unfortunately, lawyers can convince many juries that a doctor who failed to perform some esoteric test -- even if medically unjustified for the illness being treated -- must be found guilty of negligence.

Remember the Cadillac employer who persisted in undergoing medical tests until something abnormal was allegedly found? Well, after two years of abject suffering, he finally decided to seek a second cardiologist's opinion. The vector-cardiogram was repeated, along with some other tests known to be accurate. The second (and later a third) opinion was that there was no evidence of any heart disease. The patient was told he could return to his former life-style without fear. He has since lived comfortably. With the help of his new doctor, he sued the cardiologist for clouding his future with the fear of imminent death on the basis of an unverified false-positive test result. In court, no tangible proof of heart pathology could be offered and the patient collected a well-deserved sum of money to compensate for the misery one medical test caused him to endure.

Cathey Pinckney is health and medical editor for cable TV's Vector Consumer News. Dr. Edward Pinckney is a fellow of the American College of Physicians and a former editor of The Journal of the American Medical Association. They are the authors of "The Patient's Guide to Medical Tests," from which this article is adapted.