4 principle of assessing the real benefits and harms of treatment

Turning to health care, we hope to solve your health problem or at least get more good than harm. However, as can be understood as a great benefit and how much harm can bring a cure? How to decide whether or not you accept the proposed treatment or undergo examination, and how to save your money and time?

no short and simple answers to these questions. Nevertheless, the principles listed in this article will help you better understand the information about the real benefits and risks of medical services and make more informed medical decisions.

1. Do not forget about the denominator

Consider the following sentence:

Studies have shown that treatment with X reduces the risk of severe illness by 50%.

Related posts often circulate on television and in other media. Conventional medicine offers patients a wide range of services and drugs that can be described in this way.

Would you like to take this treatment? It seems that the answer should be "definitely yes", however, it is not so simple.

Reducing the incidence by 50% in people taking the drug X, it seems convincing proof of its effectiveness. In fact, this message says almost nothing about the real value of such treatment and whether you should be taking it. We can not properly understand this message, because it does not say how often the disease progresses without treatment.

How it works

Imagine the following situation:

In a group of 1000 people untreated severe disease occurs in all people. If all people taking the medication X, half of them manage to avoid the development of a dangerous disease.

500 / 1 000 × 100% = 50%.

In this situation, there is no doubt that the drug X is very valuable. Only relatively few of the currently available medical interventions have a high efficiency.

Now imagine another situation, more close to reality. In a group of 1000 people without treatment, the disease only two people develops. When all the people (one thousand) to accept treatment, the incidence is reduced by half - from two to one person per 1 000.

Although as a result we obtain a relative reduction in the incidence of 50% (1/2 × 100% = 50%), due to low incidence of the disease in people who do not take the treatment (the denominator), the medicine is not so attractive.

The useful

If your doctor or pharmacist offers to take preventive treatment or undergo checkup, ask him:

1. Why do you think I am at risk?
2. How likely is it that I get sick if I do not take medication or do not pass inspection?
3. Exactly how this medicine (examination) can help me?
4. How likely is it that the treatment (examination) will be useful, and how likely it is that it will bring harm?

2. Try searching for indicators expressed in absolute values

Now public and private clinics, patients are offered a variety of services to small advantage: Screening for breast cancer, prostate cancer, aneurysms of the aorta and other. Unfortunately, there are cases where, instead of adequately informing patients afraid of the possible consequences or shame for inattention to their health.

To protect yourself from such manipulation, it is important to learn to understand how great the real benefits and real harm services. Even if enough attention and training, we are able to understand percentages and statistics, our minds are ill-suited to the treatment of such information. Throughout human people do not have most of history to deal with this type of information, and therefore it is easy to cause us cognitive distortions.

Much more familiar and so much more clear for us is the information provided in the form of absolute values ​​or the natural frequency of events.

How it works

EXAMPLE 1 №

We translate the familiar example of the effectiveness of the drug X in this format:

Without treatment, the disease develops in two people from 1000. This is the natural frequency of the disease.

When 1000 people are on treatment:

• one person with treatment possible to avoid the development of serious illness;
• one person becomes sick, despite treatment;
• 998 people receive treatment is useless, because even without treatment, they never would have developed the disease.

This format of presenting information more transparent and clearly display all important outcomes: how many people and how much treatment has helped people take the medicine in vain.

The use of many medical services is large and obvious. It is difficult to overestimate the value of treatment for injuries, some dental services, vaccination, treatment of acute infections and others. At the same time, many other medical services have only border utility. Some of the advanced features of early diagnostics of oncological diseases are beneficial only to one or more people from 1 000-2 000 patients.

EXAMPLE 2 №

The results of large randomized trialsCkrining for breast cancer with mammography It shows that preventive mammography reduces the risk of death from breast cancer by 15-29%. This does not mean that screening for breast cancer is the clear choice for all women, and that women who do not pass it lightly to their health.

Since a group of 1000 women aged 50 years in the next 10 years from breast cancer kills about six, the real benefit of the following tests:

• For 10 years, it helps to prolong the life of one or two women from 2000 due to the earlier start of treatment.
• The remaining 1998 women will take it is useless, and some of them suffer because of imperfectionThe possibility of defense against breast cancer (breast cancer) mammography.

Taking into account the clear evidence of the effectiveness and adverse effects of the preventive mammography, it becomes clear that the decision to hold the screening of breast cancer is not a straightforward. If women do not see the benefit in this survey, they have every right to refuse it, and no one has a factual basis to call them irresponsible for such a decision.

EXAMPLE 3 №

Similarly is the situation with the screening of prostate cancer in men. Systematic Survey of men aged 54 to 69 years over 13 years is associated with reduced risk of death from prostate cancer by 30%Reconciling the Effects of Screening on Prostate Cancer Mortality in the ERSPC and PLCO Trials.

But aggressive form of prostate cancer are relatively rare, and after transfer to a more transparent form of the figure indicates the following:

• If 1000 men aged 54-69 years, will take the PSA analysis once every few years for 13 years, it is examination will significantly extend the life of one or two men due to more early detection of aggressive form of the disease. Predict who among 1000 men receive this benefit, it is impossible.
• For the rest of 999-998 men survey will be useless in this group, and some men sufferThe ability to protect against prostate cancer by PSA screening.

Thus, in the case of prostate cancer screening, too, the final decision is not obvious, it can take only the man himself.

EXAMPLE 4 №

A proper understanding of statistics is necessary in other situations. For example, when patients are afraid to use the funds that bring significant benefits at relatively low risk.

In the medical literatureHelping Doctors and Patients Make Sense of Health StatisticsDedicated to the interpretation of statistical indicators, it is often considered the incident in England in 1995. After the British Committee on Safety of Medicines (U.K. Committee on Safety of Medicines) said that "the use of combined third-generation contraceptives increases the risk of deep vein thrombosis feet by 100% ", many women were scared and stopped taking these contraceptives.

Thrombosis can be dangerous, as the migration of a thrombus can lead to blockage of the major blood vessels (thromboembolism) and death. However, as was in fact justified panic and helped the women whether the rejection of the combined contraceptive better care of yourself?

The results of studies in which it was observed increase in the risk of thrombosis, were as follows:

• Women who take the combined second-generation contraceptives, thrombosis developed a rate of one case per 7000 women.
• Women who took the third-generation contraceptives, thrombosis developed with a frequency of two cases per 7000 women.

Thus, in a group, use the combined contraceptive third generation, the relative risk score thrombosis indeed increased by 100% (twice), however, the absolute increase was one additional case 7000 women.

The ensuing wave of rejection of the message of combined contraceptives has led to nearly 13,000 unwanted pregnancies, Including among adolescents. And most importantly, women who become pregnant after the rejection of contraception, not only did not reduce their risk of thrombosis and embolism, but increased it. The fact is that during pregnancy the risk of thromboembolism is almost three times higher (around 29 cases per 10 000 women) than when using combined oral contraceptivesCombined contraceptives in the form of tablets, skin patches and / or vaginal rings. Evidence-based information for women.

This example shows that the information provided in the form of a natural frequency of events, allows more adequately assess the real benefits and real harm of drugs and other medical services.

The useful

To be able to select the services that you really interested in, and form realistic expectations with respect to medical care, need to learn to ask their doctors the right questions:

1. What happens if you refuse an examination or treatment?
2. How urgent need to conduct an examination or treatment?
3. What scientific data confirm the usefulness of the services offered?
4. What harm can bring these interventions?
5. Can you solve some other problem way, including cheaper or safer?

The doctor should give reasoned answers to these questions. More detailed guidance on the medical decisions given in this article.

3. Make sure that, if used in a statement the same comparison group

When you offer some kind of treatment, especially in the guise of innovative techniques, ask and risk Make sure that information about the different outcomes were expressed using the same groups comparison.

How it works

Consider the following message:

Treatment helps 10 patients from 1000, but it causes serious side effects in two patients out of 100.

At first it may seem that more patients receive treatment benefit than harm. In reality it is not. Due to the use of different comparison groups and our natural tendency to ignore denominators message causes severe cognitive illusion.

Everything becomes clear if we bring performance benefits and harm to a common denominator, such as 1000:

Treatment helps 10 patients from 1000, but causes serious side effects in 20 patients out of 1000.

It turns out that the real risk of treatment twice its benefits.

To facilitate comparison of indicators presented as fractions with different denominators can also translate the fraction into a percentage.

For example, compare the fractions 1/5 and 1/9:

• 1/5 × 100 = 20% (20 out of 100 people);
• 1/9 × 100 = 11% (about 11 out of 100 people).

The useful

Fortunately, only a few medical problems require urgent action really. If the solution to the problem may be delayed for some time, it can be very useful:

1. More to explore it by comparing information from different sources.
2. Compare the advantages and disadvantages of various options.
3. Learn a second opinion.

4. Note the emotional frame of the message and try to change it

Imagine this situation:

Patients are asked to choose between surgery and rehabilitation treatment. During the consultation the doctor reports that killed one patient out of 100 during the operation due to complications.

How do you feel about such an operation?

Now imagine that the doctor said: "Safety of operation is 99%; of 100 patients who undergo surgery, in 99 patients all goes well. "

It may seem that in the latter case we are talking about some other operations, but from a mathematical point of view, both are equivalent posts. It differs only in their emotional framing.

How it works

We are much more serious about the messages formulated in a negative emotional frame, especially if we are talking about the possibility of a catastrophic lossHelping Patients Decide: Ten Steps to Better Risk Communication. In the prehistoric past, such an adaptation is likely to help people to be more careful and to survive, but in this we are increasingly there is a need to reconsider how useful such installation.

Faced with a message, formulated in a one-sided manner, try to reformulate it in such a way to include all the important outcomes:

Of the 100 patients who go through surgery, one patient dies, and at 99 if everything goes well.

Negative emotional wording often used by supporters of the anti-vaccination movement. To justify its position, other than pseudo-scientific conclusions, they also use emotional manipulation. They focus the audience's attention to the extremely rare cases of children affected by the receipt of vaccinations, and ignore the other, the positiveVaccines to Children: Protective Effect and Adverse Events: A Systematic Review piece of history - a huge number of children whose vaccination was normal, and that thanks to it obtained protection from dangerous infections.

The useful

When you need to make medical decisions, try to switch attention to the emotions by numbers and facts. To learn this, work-out themselves in different ways of presenting information.

Total

The use of these principles is not how to find the right decision (in fact it does not exist), but rather, to make a decision that will most suit you, based on your attitude to risk and the goals that you set for medicine.

Of course, this is not an exhaustive list skillsNeeded for better medical decisions, however, the possession of these skills will allow you to have better orientation among the masses of health messages and services.