Before embarking on the development of a lateral flow assay, the critical requirements of the assay you are going to produce should be outlined. Assays are designed based on these requirements which are referred to as “Design Requirements” or “Design Inputs”. Design Requirements typically describe the function, performance, usability, and safety requirements of the assay in relation to its intended use. Ultimately, these requirements will provide a framework for all future development work. Examples of design requirements include quantitative or qualitative results, limits of detection, dynamic range, and shelf life. A typical assay development pathway follows this figure:
In this module we will be focusing on the first section, “Establish General Design Requirements”, and the role it will play with the “Assay Optimization” step.
Assay design requirements are claims that are to be comprehensive, unambiguous, non-conflicting, and measurable. Developing design requirements necessitates a comprehensive understanding of the assay's purpose. For development of a commercial test, it is recommended that a Customer Needs Report is first drafted. This document will detail the functional needs, handling needs, as well as the diagnostic requirements of the test based on feedback from the target market. If the assay will be generating data that has medical significance, the assay is likely subject to review by organizations such as the FDA before it can be sold commercially. Once the assay is developed, the performance of the assay will be measured against these requirements in validation and verification studies.
Before any feasibility tasks begin, the first thing that needs to be done is to develop a comprehensive list of the general requirements for the assay based on the intended use. These requirements are very basic, and will serve to provide guidance during the development process. Requirements are written by listing out specific requirements (e.g. Assay Run Time), followed by the description/claim (e.g. the test will produce a reliable result for the concentration of hCG in < 25 minutes). When nanoComposix helps develop Design Requirements with our customers, we begin with the following:
There are many more requirement categories not listed above which should also be considered (e.g. Packaging, Shipping, Labeling, Regulatory, and Safety). It is never too early to make sure all requirements are considered to avoid future project delays.
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Example Design Specifications |
Once design requirements have been defined, this will allow for a more characterized development plan with measurable milestones. The next step is to begin optimizing the assay to meet these requirements. The sequence of modules that follow will help you through this early development phase. During the optimization process, you may find that new requirements need to be added while others will need to be adjusted or removed all together. This is very typical of the process, and important to developing the right requirements moving forward. The list of design requirements should be a living document that continuously evolves throughout the process of optimization. Optimization will eventually lead you to a point where you can effectively demonstrate that you have developed an assay that can meet all the requirements needed for a successful product.