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USP 161

Nano-Test® > Research > Standards > USP 161

USP <161>

USP <161> is one of the general sections published by the United States Pharmacopeia (USP) and bears the full title ‘Transfusion and Infusion Assemblies and Similar Medical Devices’. The section defines the test requirements and acceptance criteria for assessing the physicochemical and biological suitability of medical devices that come into contact with blood, blood components or infusion solutions (e.g. blood donation/transfusion sets, infusion sets, syringes, needles, catheters, blood bags, filters, connectors, tubing and similar plastic/elastomer components). to assess their physico-chemical and biological compatibility

Note on regulatory status: The general sections of the USP are among the officially recognised standards (official compendia) in the United States under the Federal Food, Drug and Cosmetic Act; and are frequently referred to in FDA applications (510(k), PMA, IND/NDA) as well as in declarations of compliance with the US Pharmacopeia. As chapter numbering and text content may be updated through regular revisions of the USP-NF, the current edition of the USP-NF and, where applicable, the Revision Bulletin/Commentary should be checked before work commences. The following content reflects the general framework of the chapter; the current USP-NF text is authoritative for acceptance criteria and test details.

The relationship between USP <161> and ISO 10993: Both frameworks aim to assess the biological safety of medical devices; however, their approaches differ. ISO 10993-1 focuses on the selection of endpoints using a risk-based, evidence-based approach, whilst USP <161> provides a more prescriptive test battery and classification system. For certain products (particularly sets and components that come into contact with blood or solutions), the requirements of both frameworks may be applied in conjunction; they should be assessed together, taking into account the test strategy, target market and regulatory expectations.

Scope and classification of products

Products falling within the scope of USP <161> are generally assessed according to the nature and duration of contact. This section is based on the classification of plastic materials in accordance with the tests set out in USP <88> (Biological Reactivity Tests, In Vivo) (a system generally known as Classes I–VI) and on the test requirements corresponding to these classes. The class reflects the degree of biological reactivity of the material and forms the basis for assessing the product’s suitability for clinical use. Details of the classification and approval criteria can be found in the current USP-NF text.

Physico-chemical tests

This section describes tests for assessing substances that can be extracted from the materials of the medical device, as well as the properties of those materials. Parameters frequently covered include:

  • Extractable substances: extraction under specific conditions (e.g. using water, alcohol or suitable solvents at a defined temperature and for a defined duration) and assessment of the extract
  • Non-volatile residue: The amount of residue remaining after the extract has evaporated
  • Residue on ignition: Assessment of the inorganic residue
  • Heavy metals: Comparison of the presence of heavy metals in the extract with limit values
  • UV absorption: Assessment of the extract’s absorption in the 220–340 nm range
  • pH change and buffer capacity: Effect of the extract on the pH value
  • Reducing agents: Assessment of the reducing components in the extract
  • Extractable metals: Elemental analysis where necessary

Biological tests

This section refers to other general sections of the USP for the assessment of the biological reactivity of materials and devices:

  • USP <87> – Biological Reactivity Tests, In Vitro: Assessment of cytotoxicity in cell cultures (agar diffusion, elution or MEM methods)
  • USP <88> – Biological reactivity tests, in vivo: systemic injection test, intradermal test and implantation test; basis for the classification of plastics into Classes I–VI
  • Haemolysis test: Assessment of haemolytic potential in cases where the device comes into contact with blood (in accordance with the USP method or equivalent methods such as ASTM F756)
  • Pyrogenicity: Rabbit test in accordance with USP <151> (Pyrogen Test) or validated alternatives; in addition, endotoxin assessment in accordance with USP <85> (Bacterial Endotoxins Test)
  • Sterility: Sterility tests in accordance with USP <71> (where the product is supplied in a sterile form)

The key parameters reported in the study are as follows:

  • Description of the device, material composition, and the nature and duration of contact
  • USP class of the material (Classes I–VI) and justification for the classification
  • Extraction conditions (solvent, temperature, duration, surface-to-volume ratio)
  • Results of physico-chemical tests (extractable substances, residues, pH, UV, heavy metals, etc.)
  • USP <87> Cytotoxicity results
  • USP <88> Results of tests on systemic injection, intracutaneous administration and implantation
  • Results of the haemolysis test
  • Pyrogenicity / Endotoxins Results
  • Infertility results (if applicable)
  • Comparison with the acceptance criteria and evaluation of the results
  • Data on measurement uncertainty and repeatability

Why is this being done?

USP <161> wird für die folgenden wissenschaftlichen und regulatorischen Zwecke angewendet:

  • Ensuring patient safety: Assessment of the physicochemical and biological suitability of products that come into contact with blood, blood components and infusion solutions
  • USP compliance: Provision of the necessary test data for the declaration of conformity in accordance with the official compendium standards on the US market
  • Support for FDA submissions: Use as evidence of biocompatibility and material compatibility in 510(k), PMA and equivalent regulatory documentation
  • Material classification: Determination of the degree of biological reactivity of plastics and elastomers in accordance with the USP classification <88> and definition of suitable areas of application
  • Assessment of the extract profile: identification of substances that may be released from the medical device and comparison with the acceptance criteria
  • Ensuring haemocompatibility and the absence of pyrogens: Assessment of the haemolysis and pyrogenic potential of blood-contacting products
  • Ensuring sterility: Verification of sterility requirements for products supplied in a sterile state
  • Product development and supply chain: Assessing the impact of new materials, changes in suppliers and process changes
  • Quality control: Monitoring consistency between production batches
  • The ‘evidence-weighting’ approach: a contribution to the holistic assessment of the product in conjunction with the ISO 10993 series and other biocompatibility data

USP <161> deckt allein nicht das gesamte Biokompatibilitätsprofil des Produkts ab; für Endpunkte wie lokale Gewebeeffekte, Sensibilisierung, Genotoxizität und Implantation können die ISO-Normen der Reihe 10993 sowie andere relevante Normen erforderlich sein. Die Teststrategie sollte unter Berücksichtigung der Art und Dauer des Produktkontakts sowie der regulatorischen Ziele gemeinsam geplant werden.

Als NanoTest führen wir die physikalisch-chemischen und biologischen Bewertungen im Rahmen von USP <161> mit wissenschaftlicher Sorgfalt auf der Grundlage unserer akkreditierten Laborinfrastruktur und unseres Qualitätsmanagementsystems durch.

Für Informationen zu Teststrategien, Materialklassifizierung, Extraktionsbedingungen, Testzeitplänen und Berichtsprozessen im Zusammenhang mit Ihren physikalisch-chemischen und biologischen Bewertungen gemäß USP <161> können Sie sich gerne an NanoTest wenden.

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