Diagnostic Test Principles: Overview and Applications for Pain Medicine

Research Article

Phys Med Rehabil Int. 2014;1(1): 8.

Diagnostic Test Principles: Overview and Applications for Pain Medicine

Upadhye S1 and Kumbhare DA2*

1Department of Emergency Medicine, McMaster University, Canada

2Department of Medicine, University of Toronto, Canada

*Corresponding author: Kumbhare DA, Department of Medicine, University of Toronto, Canada

Received: July 03, 2014; Accepted: July 20, 2014; Published: Aug 01, 2014


Patients frequently present with undiagnosed medical complaints. Physician's assessments involve a history, physical examination and review of relevant investigations before arriving at a diagnosis. We present a clinical scenario of lower back pain and assist in the derivation of the diagnosis based upon information available in the literature. Common clinical issues are discussed from a statistical decision perspective with aids for the busy clinician. The need for diagnostic tests in decision making is discussed with an outline of key concepts such as measures of test efficacy, recognizing biases in diagnostic studies, critical appraisal tools. Common clinical situations such as ordering a test for patient reassurance, over-reliance on a diagnostic test are also discussed.


Patients frequently present to their physician with undiagnosed medical complaints, and it is up to the physician to clinically assess these patients and undertake treatment plans. Part of this process includes doing a proper history, physical examination, and ordering further diagnostic tests as warranted. Diagnostic tests can be useful to help confirm or refute a medical diagnosis (in conjunction with clinical judgment), determine the severity of disease, and/or evaluate responses to treatment once a diagnosis has been made [1]. It is imperative to understand that diagnostic testing should not replace clinical judgment, as the test results may not be infallible, and if interpreted incorrectly, can be misleading. A key tenet of diagnostic testing is that tests should be ordered ONLY when there is a potential change in management decision-making, not just for the sake of confirming that which the physician already knows or is planning to do, or to put the patient at ease.

Case Scenario

You have been referred a patient with non-traumatic Low Back Pain (LBP) for further assessment and management from a community nurse practitioner. You complete a thorough history and physical examination, and determine that there are no "red flags" for low back pain that merit emergent hospital referral [2]. On further questioning, there is reluctance to go back to work and there are some obvious "yellow flags" for long-term disability, chronicity or work loss [3]. Finally, there are no objective findings of neurologic deficit that merit immediate advanced imaging.

You and your patient agree on an initial conservative management plan, but the patient would like confirmatory diagnostic imaging just to "see what's going on." You explain that there is no role for X-rays or CT scan due to their lack of utility in non-traumatic LBP (and potential harms). The patient then pushes you to order an MRI. You know this is not warranted at this time, as this is contrary to current LBP guidelines [2], and have been over utilized for LBP in Canada [4]. Furthermore, you don't feel an MRI will change your initial management plan, and the patient may be fishing for a diagnosis to justify a disability claim submission. You discuss this with your patient.

Key Reference

You are concerned that your otherwise healthy patient may be looking to go on disability and not return to work. You are aware of a recent review on this concern regarding predictors of persistent chronic disabling low back pain [3]. The key results from this systematic review are summarized in Table 1.