Screening vs diagnostic tests : 12 major differences and top important MCQs

Introduction

Screening tests and diagnostic tests serve different purposes in healthcare:

• Screening tests are used to identify potential disease in asymptomatic individuals. They are usually less invasive, widely applied, and meant to detect early signs of disease. A positive result often requires further diagnostic testing.
  • Example: Mammography for breast cancer screening.
• Diagnostic tests are used to confirm the presence of a disease in individuals who have symptoms or a positive screening result. They are typically more specific and may be more invasive or expensive.
  • Example: Biopsy to confirm breast cancer after an abnormal mammogram.

In short, screening detects risk, while diagnosis confirms disease.

Table of differences Screening vs Diagnostic tests

Feature	Screening Test	Diagnostic Test
Purpose	Detects potential disease in asymptomatic individuals	Confirms disease in symptomatic individuals or those with positive screening results
Target Population	Large, general population at risk	Individuals with symptoms or positive screening results
Timing	Performed before symptoms appear	Performed after symptoms appear or after a positive screening test
Outcome	Indicates the need for further testing	Provides a definitive diagnosis
Invasiveness	Usually non-invasive	Can be invasive
Cost	Generally lower	Often more expensive
Accuracy	High sensitivity (to detect most cases) but may have false positives	High specificity (to confirm disease with accuracy)
False Positives/Negatives	More false positives (may identify healthy people as at risk)	Lower false positives but higher false negatives in some cases
Follow-up Needed?	Yes, a positive result requires further diagnostic testing	No, provides a final diagnosis
Repetition	Performed at regular intervals (e.g., yearly)	Done once or as needed for confirmation
Population-Based or Individual-Based?	Population-based	Individual-based
Example – Cancer	Mammogram for breast cancer screening	Biopsy to confirm breast cancer
Example – Infectious Disease	HIV rapid test	Western blot or PCR test for HIV confirmation
Example – Pregnancy	Home pregnancy test (detects hCG)	Ultrasound to confirm pregnancy location and viability

MCQs on Screening vs. Diagnostic Tests

1. What is the primary purpose of a screening test?

A) To confirm the presence of a disease
B) To detect potential disease in asymptomatic individuals
C) To provide treatment for a disease
D) To identify the severity of a disease

2. Which of the following is an example of a screening test?

A) Biopsy for cancer
B) Blood glucose test for diabetes symptoms
C) Mammogram for breast cancer in healthy individuals
D) MRI scan for severe headaches

3. Screening tests are usually performed on which type of population?

A) Only symptomatic individuals
B) Only individuals with family history of a disease
C) General population at risk but without symptoms
D) Patients already diagnosed with a disease

4. How do screening tests differ from diagnostic tests in terms of cost and invasiveness?

A) Screening tests are more expensive and invasive
B) Diagnostic tests are less expensive and non-invasive
C) Screening tests are usually less expensive and non-invasive
D) There is no difference in cost and invasiveness between the two

5. What happens if a screening test result is positive?

A) The patient is immediately treated for the disease
B) The test confirms the disease without further evaluation
C) Further diagnostic testing is required to confirm the disease
D) No further action is needed

6. Which of the following characteristics is typical of a diagnostic test?

A) Performed on asymptomatic individuals
B) Typically repeated at regular intervals
C) Highly specific and confirms disease presence
D) Conducted on a large population without symptoms

7. Which of the following is NOT a feature of screening tests?

A) High sensitivity to detect most cases
B) Regularly performed at set intervals
C) Used to confirm a definitive diagnosis
D) Conducted on a wide population

8. Which of the following screening tests is used for infectious diseases?

A) HIV rapid test
B) Biopsy
C) MRI
D) Ultrasound

9. Which statement about false positives in screening tests is true?

A) Screening tests rarely produce false positives
B) False positives can lead to unnecessary follow-up tests
C) False positives are not possible in any medical test
D) False positives confirm the presence of a disease

10. A diagnostic test is typically performed:

A) On all individuals, regardless of symptoms
B) On people showing symptoms or with a positive screening test
C) Only when no symptoms are present
D) To replace screening tests

---

Answer Key

1. B – To detect potential disease in asymptomatic individuals
2. C – Mammogram for breast cancer in healthy individuals
3. C – General population at risk but without symptoms
4. C – Screening tests are usually less expensive and non-invasive
5. C – Further diagnostic testing is required to confirm the disease
6. C – Highly specific and confirms disease presence
7. C – Used to confirm a definitive diagnosis
8. A – HIV rapid test
9. B – False positives can lead to unnecessary follow-up tests
10. B – On people showing symptoms or with a positive screening test