Biomedical Engineering Reference
In-Depth Information
3.5 ANALYTICAL VALIDATION OF BIOMARKER ASSAYS
The ICH Harmonised Tripartite Guideline of 1996 states that “the main objective of
validation of an analytical procedure is to demonstrate that the procedure is suitable
for its intended use” [26]. Many papers have been published detailing the parameters
(e.g., precision, accuracy, recovery, stability, specificity, etc.) that should be evaluated
during assay validation. The majority of these have focused on assay validation in the
bioanalytical laboratories that support measurements of drug concentrations [27, 28].
Today most analytical laboratories involved with measurement of biomarkers are
quite familiar with these validation parameters and many laboratories document
biomarker assay validation in formal validation reports ([29, 30]; Table 3.1). Many
pharmaceutical companies have instituted biomarker assay validation committees
to oversee the approval process of the analytical validation of proposed biomarker
methods. This scrutiny of the validation of the analytical tools has clearly increased
the quality of the biomarker methods used in clinical development.
The ultimate outcome of the analytical validation of a biomarker method is to
understand the limitations of the analytical method, but this goes beyond the char-
acterization of the analytical method. It is of utmost importance to understand the
sources of biological and preanalytical variability, such as the stability of the biomarker
after sampling, and the influence of biological variability, such diurnal/seasonal effects,
effects of food intake, physical activity, posture, and so on [23, 30]. The biological
variability in a biomarker should be assessed in clinical studies where the subjects are
well controlled. Some of the most controlled clinical studies are the very first clinical
development studies, the so-called single ascending dose (or first-in-human) studies, as
well as some of the early multiple-dose studies. All subjects in most first-in-human
studies are usually kept under strict surveillance throughout the study; therefore, these
studies are ideal for assessing biological variability in the measured biomarker if
frequent sampling is acceptable. Figure 3.2 shows the intrasubject variability in a
biomarker in 18 healthy subjects treatedwith placebo over a period of 5 days in a phase I
TABLE 3.1 Validation Parameters for Biomarker Assays
1. Reference material (detailed documentation)
2. Analyte-response relationship
3. Biological matrix-based quality controls
4. Intraassay precision (at least five analytical runs with
3 different samples)
5. Interassay precision (at least five analytical runs with
3 different samples)
6. Sample stability (collection, processing, storage, and shipping)
7. Accuracy/specificity
8. Recovery from biological matrix
9. Dilution linearity
10. Reportable range
11. Evaluate potential interference by test drug
12. Reference range for pertinent population(s)
13. Method comparison (when possible)
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