Which of the following would be variations of a Diagnostic test process?

• A. Patient cannot tolerate the test
• B. Patient is not compliant with preparatory instructions
• C. Test returns a false positive
• D. Test is conducted by referral to an external facility

Answer: (D)

Variations in how a diagnostic test is carried out include changes in where or how the test is performed, not the outcome of the test itself. When a test is conducted by referral to an external facility, the testing occurs outside the usual in-house setting, involving different workflows, coordination, and data transfer. This is a clear example of a process variation because it changes the delivery pathway of the diagnostic service.

The other scenarios describe factors that affect the test’s execution or result but aren’t variations in the test delivery process itself. If a patient cannot tolerate the test, or cannot follow preparatory instructions, these are patient-side or operational challenges, not a different way the test is performed. A false positive relates to the test’s accuracy characteristics, not a change in where or how the test is carried out.

So, referring the test to an external facility represents the variation in the diagnostic test process.