Medical diagnosis: process & pitfalls


Senior Member
Aug 13, 2009
Medical diagnosis: process & pitfalls

K. S. Jacob, January 6, 2010

Understanding the diagnostic process can help both physicians and patients make the best decisions related to health. Photo: K.R. Deepak

Arriving at a medical diagnosis is a complex process requiring clinical skill. The need for clear decisions has to be balanced by an acceptance of the ambiguity of the situation.

Most patient-physician interactions result in a diagnosis or are a follow-up on decisions made. Diagnostic conclusions are a routine in clinical practice, have major implications for the patient, and will determine subsequent therapy. However, many patients rarely appreciate the complexity of the process, which is also frequently misunderstood by physicians.

Clinical demands: A doctor is required to make clear decisions based on an unambiguous estimate of the problem. Patients usually seek and physicians often provide a definitive diagnosis and this works well in practice. However, often, the clinical picture is ambiguous, making it difficult for physicians to reach a definitive conclusion. In such situations, the possibility of a mistake is real and is a common professional hazard. Rather than accepting the ambiguity of certain clinical situations and explaining it to patients, doctors are often pressured to make definitive decisions in unclear circumstances. Situations, which actually demand a probabilistic inference due to the incomplete and fragmentary nature of information, are often discussed in terms of clinical certainty, forcing errors.

Diagnostic process: The traditional view of the diagnostic process is one of analytical reasoning, which includes the generation of hypotheses, their testing and verification based on patient data, through a conscious deductive process. Recent research argues for non-analytical reasoning among skilled physicians, based on pattern recognition, a process that is intuitive and matches the clinical pattern with memory. The ability to focus on important clinical issues and see the big picture requires clinicians to separate the wheat from the chaff. Classical presentations of uncomplicated disease are diagnosed by pattern recognition, while complex problems require analytical thought in addition.

Experts realise that the context has a more powerful influence on diagnosis than clinical data. Often, the probability of a common disease presenting itself atypically is higher than that of a rare disorder. Knowledge of the background of a patient (age, sex, family history) and local conditions make it possible to reach the correct diagnosis. Skilled physicians follow patterns of symptoms to make appropriate conclusions. They do so, reversing the approaches adopted in medical texts, which are most often organised around disease categories rather than on clinical presentations.

Logic of medical diagnoses: Formal logic is deductive. For example, two plus two is always four within the closed system of mathematics. In contrast, inductive logic (Bayesian), employed in medical diagnosis, does not have the same degree of certainty, as it moves from a set of specific facts to a general conclusion. For example, all observed crows are black, so all crows must be black.

Such a conclusion is convincing and probable, but not necessarily factual or binding. For example, conclusions drawn from studying problems in 100 patients with a particular disease are used to diagnose and predict issues in the 101st patient presenting with similar problems. Such a process is inherently prone to error.

Clinical reality and gold standards: The standards for diagnosis of varied diseases are different. While some conditions are diagnosed based on pathology obtained by biopsy, others rely on radiological and laboratory tests or clinical signs, which are surrogate markers for tissue pathology. In addition, the results of many diagnostic tests employed in clinical practice are sharply divided as positive or negative. Despite their mathematical and clinical convenience, dichotomous demarcations often misrepresent clinical reality, which can lie on a spectrum, leading to errors.

Definite, contributory and surrogate evidence: The evidence generated by medical procedures contributes different weights to diagnosis. Certain procedures, such as a liver biopsy for hepatitis, produce definitive evidence. Others, such as the elevation of the enzyme creatinine phosphokinase in a patient with suspected myocardial infarction, provide contributory evidence. When combined with clinical history and electrocardiographic data, the results of the test can lead to a diagnostic decision. There are many easy and inexpensive procedures, which are surrogate and substituting for more definitive tests, and are employed to screen for different conditions. Those positive on such screens are subsequently confirmed using an expensive or elaborate test.

Statistics of agreement and prediction: A surrogate or screening diagnostic test is judged by its agreement with the gold standard. Many tests have reasonable indices or averages, which reflect the number of people with disease who are identified by the test (sensitivity) and the number of people without disease who are test negative (specificity). However, the predictive value of a test, when applied in practice, is dependent on the prevalence of the condition in the population tested.

Tests used in groups with a low prevalence of the condition to be detected would produce high false positive rates. For example, diagnostic tests like the VDRL for syphilis, when employed indiscriminately, will result in poor prediction and errors. The test should be applied only in patients who report a history of unprotected sexual exposure, as this would artificially raise the prevalence of the condition in the group being tested. Similarly, indiscriminate use of screening tests in groups with a very high possibility of a condition (like clear signs of a disease) results in high false negative rates. The clinician’s assessment of disease probability in the individuals tested is important. There should be a reasonable uncertainty about the presence or absence of the disease before the surrogate test is ordered for the most optimal interpretation of results.

The degree of diagnostic certainty needed in making clinical decisions is also a function of the degree of risk presented by the therapeutic options. For the use of specific therapy, which is highly efficacious and has a low level of risk of adverse effects (example, the use of vitamin supplementation in pregnancy), few tests are needed because physicians can accept substantial diagnostic uncertainty. On the other hand, in situations where treatment options are less effective and carry a greater risk of side-effects (as in cancer), clinicians often need a higher degree of diagnostic certainty.

Hindsight and diagnosis: There is no such thing as a perfect diagnostic system; improvements made often have a trade-off. Highly sensitive systems overdiagnose conditions while blunter investigative methods underestimate the risks. The trade-off is essentially between sensitive systems, which give false alarms, and blunt systems, which do not pick up the condition concerned. The diagnostic challenge for physicians is to separate the signal from background noise.

A missed diagnosis is always clear with hindsight. The thread connecting relevant information, which was missed or misinterpreted, can be found but prior to the final discovery, the big picture may form an indistinct pattern. This has been described as “creeping determinism” where the occurrence of an event increases its reconstructed probability and makes it less surprising than it would have been had the original probability been kept in mind. Such creeping determinism later becomes unfair criticism of the diagnostic process. In actual practice, clear diagnostic stories may be less frequent than realised. Nevertheless, medical negligence needs to be differentiated from errors made due to the ambiguity of the clinical situation.

For better understanding

Physicians often prize the production of evidence-supported narratives of diseases. They rarely examine the probabilistic nature of the process of diagnosis. All doctors make mistakes, have weaknesses, and expertise is not a static but dynamic state. Good clinicians regularly review patient data, revalidate the patterns identified, examine the probabilities and have the courage to question their earlier diagnostic interpretations allowing them to reassign risks and diagnoses.

Poor clinicians fail to understand the process and repeatedly make the same errors in judgment. There is need to refocus on improving clinical skills and on the judicious use of diagnostic tests. The journey to exceptional expertise is not for the faint-hearted or for the impatient, and it is a continuous quest for excellence.

It is often difficult for patients to evaluate the evidence and arrive at definitive conclusions. Choosing physicians with clinical skills, asking for the evidence and reasoning behind decisions, accepting the ambiguities of the clinical situations and agreeing to a regular review are crucial. Physicians and patients should realise that judicious use of second opinions in situations, where the implications of diagnostic procedures, the diagnosis and treatment are grave, may be necessary.

The challenge is to integrate the science and the art of clinical medicine. Understanding the diagnostic process can help both physicians and patients make the best decisions related to health.

(Professor K.S. Jacob is on the faculty of the Christian Medical College, Vellore.)

The Hindu : Opinion / Lead : Medical diagnosis: process & pitfalls


Senior Member
Aug 13, 2009
Changing cultures within medicine

K. S. Jacob, December 8, 2009

CHANGE FOR GOOD? Medicine today looks less of a vocation and more of a business opportunity.

The changing cultures within medicine, with the focus on disease, cure and specialist approaches, prefer costly technology and profit to clinical evaluation, holistic care and service.

Medicine continues to be a valued career choice in India. However, the many changes in society over the past few decades have made it a less attractive option today. The changes in the social and financial climate have also resulted in major shifts within medicine. The changed culture within medicine appears pervasive and, in many ways, irreversible. Medicine today looks less of a vocation and more of a business opportunity.

Many recent changes, some subtle and others more obvious, have had a significant impact on the practice of medicine. Even subtle shifts within society have had a major impact on the traditions of medicine, with some catastrophic and others no less monumental.

Prevention versus cure

Prevention is less fashionable than cure: employing urgency-driven curative medical solutions, instead of long-term public health policies, is common. Diarrhoea, potentially a killer disease among the vulnerable and often caused by unsafe water and poor sanitation, is commonly treated with antibiotics with no provision to address the root causes. This is also true for the relationship between tuberculosis and poor housing or chronic malnutrition and inadequate nutrition. Much of the effort of today’s champions of public health ends up in provision of curative services, albeit at the small hospital or clinic. They succumb to the constant demand for better curative services. Such services thwart public health efforts by treating diseases and preventing death (reducing their impact on social consciousness), which should have been prevented in the first place using public health strategies. Cynics would argue that there is less money to be made through public health interventions.

Curing a disease is more glamorous than healing an illness: The medicalisation of distress has lowered the threshold for seeking help from physicians. About a third of people who visit physicians do not have a demonstrable medical disease. Many visit doctors when they are in distress or are unable to cope with life’s incessant demands. However, recent advances in technology have made diagnosis and cure attractive and profitable for hospitals and medical practitioners. Physicians are taught to focus on underlying structural and functional defects and they often tend to disregard the human context of illnesses. Many physicians, with their focus on disease and cure, get irritated with patients who present symptoms with no obvious medical causes as determined by expensive laboratory investigations. They dismiss the patients’ concerns and rarely focus on the illness or practise the art of healing.

The clinical-technology divide: Clinical assessment forms the bedrock of medicine. However, the phenomenal improvement in medical technology, while revolutionising the practice of medicine, has come at a price. It has also changed medical traditions. There is a naive belief that technology will provide answers to every clinical problem; that its widespread and indiscriminate use will do away with the need for clinical judgment. The sole reliance on technology has also resulted in a devaluation of clinical skills and the failure of the younger generation of doctors to understand its role in medical diagnosis and management.

Technology in certain situations is crucial for diagnosis and management; in others, it can complicate matters. Many diagnostic tests and screening strategies are not absolute and when applied in low prevalence situations, produce false positive results leading to further testing or unnecessary medication. For example, the electroencephalogram (EEG) is only an adjunct in the diagnosis of epilepsy, a condition that should be diagnosed based on history and clinical examination in the vast majority of patients. The EEG’s moderate diagnostic sensitivity and specificity for the condition means that it may record “abnormalities” in normal people when employed indiscriminately and be negative in those with genuine seizures. The inappropriate use of technology will mean costs in terms of not just finances but also psychological stress. The focus on technology to the exclusion of clinical assessment as practised, for example, in the United States, has resulted in an expensive and grossly iniquitous health care system.

Generalist versus specialist approaches: Over the years, the general trend has been to seek specialist advice even for minor illnesses. Such help comes at a price. The absence of a generalist who can act as a gatekeeper means that even simple problems are seen in tertiary care centres and viewed through a specialist’s lens. The specialist, with his or her perspective of excluding the rarest of rare conditions in the field, usually ends up over-investigating even the most innocuous of symptoms. In addition, the specialists’ compartmentalised view of the body often does not allow them to see the big picture and tie up multisystem problems. The lack of confidence in the basic doctor and the absence of family medicine as a speciality compound the problem.

Profit before service: The fall of communism, the rise of capitalistic thought and economic liberalisation have had a major impact on medicine and health care in India. The 1990s saw a reduction in the emphasis on public expenditure with an increase in private and out-of-pocket expenses for health care. The poor functioning of government health facilities resulted in private hospitals and medical practitioners flourishing. Medical tourism has become a profitable industry. Performance incentives in the private sector essentially imply a commission for ordering tests or prescribing branded medication and medical devices. Contracts and commissions replacing salaries also mean that there is no limit to the incomes of physicians, laboratories and hospitals concerned. The complete absence of regulation and audit in these matters often results in unethical practices. Profit before service has become acceptable. Business models and wealth are the new standards to judge the success of doctors.

Hospital and pharmaceutical industries have increased their influence on the practice of medicine. The lack of enforcement of clinical guidelines and standards and the direct conflicts of financial interests often result in unnecessary diagnostic tests and medication and increased costs.

The system of capitation fees for admission to private colleges has increased the investment in medical education. The money transactions often said to be necessary for obtaining the regulatory permissions to start and run courses are transferred by medical colleges to students and doctors. The need to recoup the investment makes those who set up such facilities and those who pass out of them look at their institutions and careers through a business lens. Many such practices, unethical and some even illegal, appear to be the norm.

The many changes have had a cumulative effect, have resulted in increased costs and reduced access to health care for the majority of the population. The iniquitous distribution of health services means the most vulnerable and marginalised, who probably are in the greatest need of health services, are unable to access them. The cost of seeking health care is known to be the single important reason for indebtedness in the country. Yet, the changed culture within society and the medical profession refuses to acknowledge the need for equity.

The way forward

The special social status accorded to physicians necessarily mandates a social commitment to serve the people, especially the underprivileged and the marginalised. Such social obligation is necessary from not only individuals but also institutions, professional medical societies, regulatory authorities and governments. There is need for social audits and for greater social recognition for those who live, work and serve in disadvantaged areas.

Selection to medical schools should also evaluate social consciousness, a record of such service and a commitment to serve vulnerable sections. In selections for higher medical education, greater weightage should be accorded to those who serve in areas of need. The commercialisation of medical education and health care needs to be checked, unethical procedures should be curbed and illegal practices rooted out.

In the changing social climate, it may be necessary to reiterate the need for social commitment from physicians. There is need to reemphasise community responsibility, to highlight service and to provide equitable access to health care for all. Surely, the special social status accorded to physicians should be acknowledged by a social commitment to the health care needs of all people, not only those who can pay. However, it is unrealistic to expect changes in the prevailing medical culture without concomitant alterations in society. The challenge is to transform the prevailing cultures within medicine and in society.

(Professor K.S. Jacob is on the faculty of the Christian Medical College, Vellore)

The Hindu : Opinion / Lead : Changing cultures within medicine


Senior Member
Aug 13, 2009
From elusive cure to enabling comfort

Ennapadam S. Krishnamoorthy, January 13, 2010

Awareness about Epilepsy at Bangalore Medical college auditorium in Bangalore. File Photo: K. Murali Kumar

We must consider quality of life and wellness as treatment outcomes and ask ourselves whether the treatment we opt for will help us achieve these outcomes.

Quality of life is a relatively novel concept that dominates both medical science and health policy today and is widely accepted as the best indicator of outcome of treatment. The focus among practitioners of modern medicine, and indeed, in social consciousness, however, remains firmly on the elusive concept of “cure.” The adage among medical practitioners of yore: “to cure sometimes, control often; but comfort always,” hints at the importance of life quality, one that is forgotten, however, in the quest for miracle cures.

That the majority of chronic conditions defy cure is something doctors know, but often choose to be agnostic of. Thus apart from infections, inflammations, metabolic disturbances and transient visitations of their ilk, that respond well to drugs designed to terminate them; and indeed abnormalities of structure (organs that have lost structural integrity) that are amenable to surgical intervention, the vast majority of medical conditions while potentially controllable, are not curable. Diabetes, hypertension, high cholesterol levels, ischaemic heart disease, stroke, epilepsy, dementia and a host of other conditions while “treatable” and/or “modifiable” (relief from clinical symptoms and attendant complications) are not “curable.” The promise of a “cure” for many chronic diseases thus remains wishful; that rainbow with its elusive pot of gold, at the end of the dark, illness cloud.

There is no doubt we are living longer as a society, and this longevity is attributable, in great part, to advances in modern medicine; cardiac bypass procedures, joint replacements, organ transplants and such like. There is ample evidence to support our collective social longevity, the average Indian lifespan having increased by over a third, since the time of independence, the increase being greater in “advanced” societies like Japan. However, whether such longevity leads automatically to enhanced quality of life remains a conjecture. For example, the follow-up data after a cardiac bypass surgery, arguably the best known lifespan enhancing procedure, shows in many studies high rates of depression and cognitive dysfunction (memory and higher order brain function problems) 5-10 years after the procedure. It would be fallacious to blame the bypass procedure for these complications in the brain and mind; after all, had the person with ischaemic heart disease lived long enough, without the procedure, he might have developed these anyway. However, in evaluating the overall “success” of such procedures or advocating their widespread application through policy implementation, these factors must be considered carefully. In this instance, the question that begs our attention is: “while the procedure enhances lifespan, does it enhance the quality of life?” And if it does not for a select group, who constitutes the group? Why not for it? When does it enhance the quality of life, and when doesn’t it? What determines the outcome in a given individual? Where and how is this outcome determined? These questions need clear answers and we do not always have them.

It is striking how both modern medicine and society are obsessed with the concept of “cure,” the quest for magic pills (or, indeed, magic procedures) that will help achieve the longevity goal, being never ending. The energy, enterprise and expense invested in this quest, by affected individuals, their families, and governments are, unfortunately, not always rewarded with a good quality of life after the procedure. Our obsession with “cure” probably comes from two very different directions. The first is idealistic; the tantalising possibility that we will, through advancements in science and technology, “fix” the vast majority of problems concerning the human body. When mankind has learnt to fly, build tunnels through mountains and under the sea, and transport itself into space at will, this aspiration of curing chronic diseases and enhancing longevity does not really seem that distant a frontier.

The second, however, probably has more sinister origins that merit careful consideration. The business of curative medicine is enormously lucrative and demands the constant creation of markets that will utilise the goods and services it develops. What could interest the human race more than the possibility of a cure for illness and life-enhancement (with or without quality)? A degree of scepticism of novel, potentially curative treatments is, therefore, warranted in the modern social context, and we must examine carefully whether the promise of “a magic cure” for any chronic condition guarantees alongside an improvement in the quality of life. Thus, while we share a collective belief that people not only live longer due to advances in medical science but also live well, the presumption of a better quality of life, is sadly, in many instances, just that — a presumption!

Scientifically viewed, the proof that many modern medical treatments enhance the life quality remains tenuous, to say the least. At a recent lecture in VHS, Chennai, Shah Ebrahim, Professor at the London School of Hygiene and Tropical Medicine and Chair of the South Asian Chronic Diseases Network, a renowned international expert on chronic disease epidemiology, rued our societal predilection for magic bullets ( The Hindu, January 9, 2010). Talking about the “polypill” — a combination of aspirin (blood thinner), a Statin (to lower cholesterol levels), and antihypertensive agents (to lower blood pressure) — that is intended to enhance cardiovascular health, he pointed out that simple health promotion measures such as changing over to rock salt from processed salt (high in sodium) and using soya oil as opposed to palm oil (which strangely attracts a lower tax probably due to anomalies in trade policy) were just as likely to improve cardiovascular health. These are far cheaper for governments to implement, and relevant to developing nations.

Prescribing the widespread use of the polypill for the middle-aged, as opposed to implementing these simple public health interventions through changes in policy, both health and trade, will be deleterious in many ways, he opined. It will be costly to the nation and poorly sustainable, will have low penetration in society and perhaps, most importantly, take away the responsibility for our health from us, placing it firmly in the hands of the pharmaceutical industry. Further, the former approach, of making people assume responsibility for their lifestyle and diet, alongside the implementation of a complementary government lead policy, is far more likely to enhance other desirable health behaviours in society and, indeed, global health outcomes.

Why do we then as a society look to the “polypill” with such enthusiasm or consider it with such seriousness? The answer probably lies in our preference for “cure” as opposed to comfort and life quality. Happily for us, improved quality of life and “wellness,” a concept that has traditionally dominated eastern thought and traditional medical systems, is today receiving much global attention. Wellness encompasses both physical and mental well-being, the latter being a dynamic state of optimal functioning referring to the individual’s ability to develop his or her potential, work productively, build strong and positive relationships with others and contribute to the community. We must recognise that the prevention and management of diabetes extend far beyond the popular notion of blood sugar control; that cardiac health cannot be achieved merely by unblocking blood vessels and enhancing circulation through a stent or bypass; and indeed that the drugs for dementia available today do not even guarantee slowing of disease progression, let alone cure or reversal.

Given this scenario, we as a nation and society must consider quality of life and wellness as treatment outcomes, quite seriously, and ask ourselves whether the treatments we are considering, however technologically advanced and seductive, will likely help us achieve these outcomes. We would also do well to examine closely the role of traditional and indigenous medical systems that have for centuries retained this focus on wellness and life quality through health promotion, prevention of illness, care and comfort for those affected with chronic illness; not merely curative treatments.

(Dr. Ennapadam S. Krishnamoorthy is Honorary Secretary, Voluntary Health Services Hospital, Chennai. The views expressed herein are his own.)

The Hindu : Opinion / Op-Ed : From elusive cure to enabling comfort

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