diagnosis
Meaning of diagnosis: Seldom a single moment, a diagnosis is usually narrowed from a list of candidates and can stay provisional for a long time.
Definition of diagnosis
A diagnosis is the identification of the disease, disorder or condition behind a person's symptoms, reached by weighing the history, the examination findings and the results of any tests against the possible explanations. The word names both the process of working it out and the conclusion recorded at the end of it.
How is a diagnosis reached?
Five sources feed into it, gathered roughly in order. The history is what the person reports: what changed, when, what makes it better or worse, together with past illnesses, medicines and family history. The physical examination adds what can be seen, felt and heard. Tests come next, chosen to answer a question the first two raised rather than collected at random. Clinical reasoning then weighs how completely each candidate explains the whole picture, and how much harm missing it would cause. Time is the fifth source and the most underrated, because many conditions declare themselves only through how they change over days or weeks.
What kinds of diagnosis are there?
| Term | What it means |
|---|---|
| Working or provisional | The best explanation so far, used to guide the next step while more information is gathered |
| Differential | The list of candidates still in play, ordered by likelihood and by seriousness |
| Definitive or confirmed | Established by a finding regarded as decisive, such as examination of tissue |
| Clinical | Made from the pattern of history and examination where no confirmatory test exists |
| Diagnosis of exclusion | Accepted only once the alternatives have been ruled out |
| Molecular diagnosis | Based on a specific genetic or molecular change rather than on appearance |
Why do some take so long?
Common conditions produce unusual presentations far more often than rare conditions produce typical ones, so an odd pattern is investigated as a variant of something ordinary before anything rare is entertained. Symptoms shared by many conditions, such as fatigue, pain or weight loss, narrow the list very little on their own. Some diseases have no confirmatory test at all and are recognized only by pattern over time. Tests are imperfect as well: a negative result lowers the chance of a condition without abolishing it, and a positive result in someone unlikely to have the condition is more often wrong than right. A diagnosis can also be revised, and a label carried for years is sometimes replaced once new information appears.
What is a diagnosis not?
It is not a prognosis, which is the expected course. It is not a symptom, which is what the person notices, nor a sign, which is what an examiner finds. And it is not the same as a cause. Naming a condition such as heart failure describes what is happening without saying why, so a second layer of the diagnosis records the underlying reason wherever one is known. The record carries weight well beyond the consultation too, since a coded diagnosis feeds statistics, research, insurance and eligibility for services.
Also known as
Used in a sentence
Further testing was needed before confirming the diagnosis.
Good to know
A differential diagnosis is not a single answer but a prioritized list of the explanations still under consideration, ordered both by how likely each is and by how much harm missing it would cause.
Word origin
Where “diagnosis” comes from
From Greek dia-, meaning through or apart, and gnosis, meaning knowledge, so literally a knowing that tells one thing from another.