An evidence-base for laboratory endocrinology?
Year: 2008
Type: article
Abstract: “Deficiencies in how research studies are reported are both well-documented and widespread across all medical specialties and study designs. Although randomised trials have received the most attention in this regard, similar concerns have been expressed about reporting of other types of research including diagnostic and epidemiological studies.”1
The use of evidence-based methods in clinical medicine has permitted considerable clarity in clinical studies and, despite the detractors of Evidence-Based Medicine (EBM), it is now possible to read research papers and decide whether, or not, they are applicable to a particular clinical scenario. A typical design might be a series of patients with a particular symptom complex who are randomised to receive different therapies; and assuming the study is sufficiently powered then the therapies can be compared. The intervention in question could be a diagnostic test and study designs have been created which allow for comparison of different diagnostic tests and strategies.2 Unfortunately their application in endocrinology has not been widely used.
Critical analysis of diagnostic procedures should be part of laboratory endocrinology since the diagnosis and management of patients with endocrine disorders is underpinned by laboratory testing. However, whilst endocrine therapies are subjected to the full panoply of clinical trial methodology followed by intensive interrogation with meta-analyses, laboratory testing is lagging behind and is accepted on a largely observational basis on selected subjects. Regrettably, there is even a move to lower the diagnostic standards in the clinical arena by attempts to simplify laboratory investigation. Examples include the preference for glycated haemoglobin rather than an oral glucose tolerance test to diagnose diabetes3 and IGF1 rather than stimulation tests for growth hormone deficiency. These proposals are controversial and have been made despite some indication that they deliver lesser diagnostic performance.
A further more demanding problem facing the development of evidence-based endocrine diagnostics is the relative rarity of some disorders e.g. Cushing’s, acromegaly, as well as the lack of clearly defined clinical “gold standards” e.g. Cushing’s, growth hormone deficiency and polycystic ovary syndrome (PCOS) which are discussed below.
The problems behind an evidence-based approach to laboratory diagnostics can be clearly illustrated by the components of a typical dynamic test used to diagnose growth hormone deficiency. These consist of 1) a variety of protocols and 2) secretagogues, 3) a variable biological response to stimulation, 4) a multiplicity of assays which differ in antibody specificity and standards and 5) finally the variability in clinical interpretation. The uncertainty produced by a combination of these factors has led to a lack of confidence in growth hormone testing that has induced a group of leading Paediatric Endocrinologists to resort to measurement of growth velocity (auxology) rather than provocative testing!4
However, prior to considering the design of investigative protocols, it is appropriate to consider the variables relevant to the analytical process. These include a number of pre- and post-analytical as well as analytical issues. Many of these aspects of the diagnostic process are fundamental and without a solution may destroy the evidence-base for laboratory endocrinology.
Source: PubMed
Author: Julian H Barth
Institution: Leeds General Infirmary
Language: English
Subfield: Medical Laboratory Technology
Field: Health Professions
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W12004016