FDA criticises Visual Inspection

During an inspection in March 2026, the FDA identified deficiencies in the programme for the visual inspection of sterile injectable medicinal products. In the Warning Letter, the authority particularly criticises the inadequate qualification of inspection personnel, as well as deficiencies in the qualification kit and documentation.

In its Warning Letter, the FDA objects, among other things, that the manufacturer's visual inspection is not suitable for ensuring that sterile injectable medicinal products are "essentially free of visible particulates". The main focus of the objection is the FDA's view that the personnel carrying out the visual inspection of sterile bags were inadequately qualified. The FDA also criticises the composition of the qualification kit used for this purpose and inadequate documentation. In the FDA's view, the qualification test kit used did not contain sufficiently representative visible particles, for example with regard to particle size. In addition, the qualification records were not sufficiently detailed to make the qualifications of visual inspection personnel traceable.

In its response to the inspection deficiencies, the company stated that the qualification kit contained representative particles and that a new kit was also being developed. The company also announced that it would regularly review production and post-market data to verify that the kit remained representative.

For the FDA, however, the response is insufficient. According to the authority, it does not address the fundamental deficiency that the qualification programme had not demonstrated that inspection personnel could adequately detect visible particles. The FDA points out that the example particles in the kit may not be representative of smaller particles that may occur in the medicinal products. The FDA explains that the visual detection of particles is, in principle, a probabilistic process. Among other things, it depends on visible particles being detected reproducibly by trained personnel with suitable visual acuity. The FDA derives specific qualification expectations from this: the qualification kit should contain particles of sizes and compositions that adequately challenge employees across the range of particle sizes that may occur in the medicinal product. As a typical requirement, the FDA states that such kits should contain particles in the range of 100-150 µm in order to adequately challenge the detection capability of visual inspection personnel.

The FDA calls for a comprehensive, independent assessment of the visual inspection programme and a remediation plan based on that assessment. This plan should improve the inspection methodology where necessary, but above all should structure qualification protocols and documentation for all inspection personnel in such a way that qualification can be demonstrated in a traceable and robust manner. The FDA also calls for the requirements of USP <790> "Visible Particulates in Injections" to be incorporated into the company's procedures and for qualification studies to be carried out with a suitable range of particle types and sizes - including particles of approximately 100-150 µm - in order to adequately assess the detection capability of visual inspection personnel.

You can find the full Warning Letter on the FDA's website.