Evidence based diagnostics: what about customary clinical tests
Christian and Lise Lotte Gluud have proposed an interesting framework for research into diagnostic tests that parallels the conventional phases in drug research . This concept is really appreciable and beneficial to all the researchers and clinicians. Predictably, the presented framework has some shortcomings and needs more developments. For instance, defining normal range based on phase I studies might be problematic in some cases as several other items should be considered for diagnostic and therapeutic thresholds (like determination of normal range for blood sugar or cholesterol). Moreover, especially for phase III and IV studies, some other issues are really important for evaluation of the results and estimation of the level of evidence, such as the setting of the study (primary or tertiary care), pretest probability of the disease, length of follow-up, and response rate to follow-up. Considering all these factors, as well as cost, availability, and invasiveness of the test, we think that a Grade of Recommendation should be defined for any diagnostic test.
However, our major concern about the quality of this framework is the group of tests targeted in it. It appears that the authors have developed the framework just for newly introduced paraclinical tests (including laboratory techniques, imaging, pathology, electrodiagnostic tests, and endoscopy). Nevertheless, another major group of tests not considered in this framework are traditional clinical tests including signs, symptoms and clinical scores. Although no one can expect a newly found or defined sign or symptom these days, the clinical utility and accuracy of most of the costumary clinical tests have not yet defined. We think that a new framework (or a modified version of the presented framework) is also required on the methods for assessing these tests.
Clinicians on their practice firstly rely on the pointers derived from clinical presentation of patients and paraclinical tests are usually considered as supplements to these signs and symptoms. Not surprisingly, in most of the cases, diagnostic accuracy of the clinical signs and symptoms have not been quantified in methodologically strong studies and physicians just trust in their own experience or some low level evidences when using these signs and symptoms in their decision-making.
We think that the major problem in the way to performing high-quality studies for clinical tests is to find funding sources. In the case of paraclinical tests, the designer or producer company is required to perform several studies to approve the test for clinical use. Using the framework proposed by the authors can standardize this process. In the case of clinical signs and symptoms, however, there is no definite foundation to fund and support such investigations. An international consensus in this regard is deeply needed. We propose that international agencies such as Cochrane Collaborations develop a similar framework and go ahead for diagnostic studies to reveal suitability of different clinical tests.
1. Gluud C, Gluud LL. Evidence based diagnostics. BMJ 2005;330:724-6
Competing interests: None declared
Competing interests: No competing interests