Why may one remain skeptical about a positive Sharp Purser test result?

• A. It indicates instability in all patients
• B. It is only validated for those with RA
• C. It confirms dissection with certainty
• D. It is a definitive diagnostic test

Answer: (B)

A positive Sharp Purser test is primarily used to assess craniovertebral instability, particularly in populations with conditions such as rheumatoid arthritis (RA). The test evaluates the stability of the atlantoaxial joint by applying posterior translation to the occiput while stabilizing the C2 vertebra.

Being skeptical about a positive result stems from the fact that this test has not been validated across all patient populations. While it is valuable in individuals with RA, the sensitivity and specificity may vary significantly in patients without this condition. Therefore, a positive Sharp Purser test result does not inherently indicate instability in all patients, suggesting that its diagnostic accuracy is limited outside of those with RA. This context highlights the importance of considering the patient's specific clinical background when interpreting the significance of the test result. Thus, the skepticism surrounding a positive Sharp Purser test is well-founded due to its limitations in generalizability.