It may be a fairly artificial abstraction, to isolate a manageable portion of a larger continuum. Chronic fatigue syndrome is a small group in the large population of people with chronic tiredness, who had a fairly sudden onset of the condition.
Sometimes a diagnosis is established by just one pathognomonic feature in the clinical picture. Koplik's spots inside the cheeks mean one thing only. This child has measles, even if the characteristic rash is yet to appear.
Sailors of yesteryear had to show their palms during inspection, as smallpox caused a rash there.
Diagnostic tests are used extensively, but are frequently misleading, putting up red herrings to draw one off the scent."Transaminitis" is a tongue in cheek term for an unexplained transaminase liver test elevation. Lumbar spine X-rays often show arthritis which has little to do with a person's backache.
"Screening tests" are valuable first steps in looking for cancer of the cervix or large bowel, but in the case of breast and prostate are of little value compared to the trouble they cause.
A selected panel of screening tests can avoid things being forgotten and may save physicians' time (and so money.) The results then have to be considered in the clinical context, to make sense of them and prevent one wasting effort on false leads.
"One of the main reasons why the treatment of enuresis brings so many bitter disappointments to patient and physician alike is the almost universal attitude of considering enuresis as a disease. Too many failures are due to this mistaken attempt to force the condition into the straitjacket of a clinical entity (single diagnostic category) and to find the single treatment which will cure all cases of enuresis - be it drug, psychotherapy or electric (read "magic") machine. Once it is recognized that enuresis is but a symptom - the underlying cause of which can be any of a widely differing variety of conditions, ranging from anatomical anomaly, through infection, metabolic disturbance, psychological disturbance, to habit - and once the cause has been identified, the first big step towards eventual cure has been taken."Lots of other "diagnoses" such as asthma, are really just descriptions of a prominent symptom (here variable airways obstruction.) Psychiatry is full of such superficial labelling.
Even if a very distinct clinical entity is diagnosed, that is only part of the story. The premorbid state of health and psychosocial functioning will have a large effect on the prognosis, even to the extent "make or break." One person with cancer will quickly throw in the towel and another will fight to the bitter end. A terminal disease diagnosis may help a person to completely turn their life around, and some people in this situation have expressed thankfulness for this opportunity.
I heard Elizabeth Kubler-Ross speak years ago, in Melbourne. She said she saw value for people to have an extended terminal illness, as it gave them more time to set things right with their circle of family and acquaintances.
"The widespread tendency among doctors is still to tend to view disease as an alien which has invaded an otherwise healthy human being. The aim of many physicians, often unstated and unrecognized as such, is to discern this alien, attach a label to it, for example appendicitis, lobar pneumonia, etc. and then to attack this alien through an effective technique, for example surgery or an antibiotic - the "concept of the magic bullet."
The emphasis is predominantly on how a patient is sick, attach a label and treat the label. The approach tends to dehumanize the patient and focus on this alien....
Increasingly today doctors are asking not only how a patient is sick, but why, and particularly why at this particular time in life."
It's worth asking yourself and asking your practitioner: why? And possibly asking the same question following the first answer: again, why? Just keep digging, to your "bottom line." This is "root cause medicine." Things like birth by caesarean section (without inoculation with your mother's intestinal microbiome) and multiple early childhood adverse experiences, are foundations of much adult illness.
"Disease is a concept that throughout history has been a product of efforts to explain and remedy ill-health. It is inextricably tied to prevailing concepts about the causes of ill-health and our ability to describe them – whether by invoking demons, curses, miasma, microbes, disturbances to energy flows or environmental toxins. Ill-health is a fact (or at least a phenomenon) but a disease is nothing more than an idea – the continually evolving nature of which is evidenced by the revision of the International Classification of Diseases (ICD) ten times in little more than 100 years."