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Prognosis vs. Diagnosis: What's the Difference?

Edited by Aimie Carlson || By Harlon Moss || Updated on October 30, 2023
Diagnosis is identifying a disease from its symptoms; prognosis is the likely outcome of that disease.

Key Differences

Let's understand that prognosis and diagnosis are terms commonly used in medicine. A diagnosis is what healthcare professionals use to identify a disease or condition based on signs and symptoms. On the other hand, prognosis refers to the likely course and outcome of the diagnosed disease.
Diagnosis is derived from the Greek word "diagnōsis," meaning "discernment" or "distinguishing." Diagnosis is crucial for determining the appropriate treatment for a patient. Conversely, prognosis comes from the Greek word "prognōsis," meaning "foreknowledge." Prognosis gives an estimation of the likely progression and outcome of the disease.
Diagnosis is a critical step in the medical process. It involves a thorough examination and often requires various tests and procedures. A correct diagnosis is essential for effective treatment. In contrast, prognosis often depends on factors such as age, overall health, and how well the disease responds to treatment.
It's important to note that prognosis can be uncertain and may change as more information becomes available. While diagnosis is usually definitive, prognosis is an educated guess based on statistics and trends. Both are essential components of the healthcare process, and they work hand-in-hand to provide the best possible care for patients.

Comparison Chart


Likely course of a disease
Identification of a disease


Greek word "prognōsis" meaning "foreknowledge"
Greek word "diagnōsis" meaning "discernment"


Future outcome of the disease
Current condition


Dependent on various factors like age, overall health
Based on symptoms and test results


Helps in understanding the disease's likely course
Essential for determining appropriate treatment

Prognosis and Diagnosis Definitions


An estimation of the likely duration and outcome of a disease.
The prognosis for patients with this condition has improved with new treatments.


The act of distinguishing one disease from another.
The differential diagnosis ruled out several potential conditions.


A medical opinion of the future course of a disease.
The prognosis was uncertain due to the rarity of the disease.


The identification of a disease or condition from its signs and symptoms.
The diagnosis confirmed that the patient had pneumonia.


The likely outcome or course of a disease.
The prognosis for the patient's recovery is very good.


The process of determining a medical condition through examination and testing.
A timely diagnosis is crucial for effective treatment.


A forecast of the likely course of a disease or ailment.
The doctor gave a positive prognosis after the successful surgery.


A medical opinion or interpretation of symptoms.
The diagnosis of the condition was challenging due to its rarity.


A prediction of the expected development of a disease.
The prognosis depends on the patient's age and overall health.


A statement or conclusion that identifies the nature of a disease.
The doctor's diagnosis was based on the test results.


Is a prognosis always necessary?

No, prognosis is not always given, especially if the outcome is uncertain.

Can a diagnosis be made without symptoms?

In some cases, yes, especially if there are significant findings from tests or examinations.

Is prognosis always accurate?

No, prognosis is an estimation and can be uncertain.

Can prognosis be positive?

Yes, prognosis can be positive, indicating a likely good outcome.

Can diagnosis change over time?

Yes, as new symptoms appear or new information becomes available.

Does prognosis depend on age?

Age can be one of the factors that influence prognosis.

Does prognosis depend on overall health?

Overall health is one of the factors that can influence prognosis.

Is diagnosis always definitive?

In most cases, yes, but it can change with new information.

Is diagnosis the same as treatment?

No, diagnosis is the identification of a disease, while treatment is how the disease is managed.

Is diagnosis always necessary?

In most cases, yes, to determine the appropriate treatment.

Can prognosis be negative?

Yes, indicating a likely poor outcome.

Can diagnosis be made without examination?

In some cases, yes, especially if the symptoms are characteristic of a specific disease.

Can prognosis change?

Yes, prognosis can change as more information becomes available or as the patient's condition changes.

Can prognosis be uncertain?

Yes, especially for rare or complex diseases.

Can diagnosis be challenging?

Yes, especially for rare or complex conditions that have symptoms similar to other diseases.

Does prognosis vary from person to person?

Yes, prognosis can vary based on a range of factors unique to the individual.

Is diagnosis based on patient history?

Patient history is an essential component of the diagnostic process.

Is diagnosis only made by doctors?

No, other healthcare professionals can also make diagnoses.

Does prognosis depend on treatment response?

Yes, how well a disease responds to treatment can influence prognosis.

Is diagnosis always based on tests?

No, diagnosis can also be based on symptoms and physical examination findings.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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