The United States is a country with many unique distinctions, with some of those ranking better (its GDP) than others (its spending on healthcare). But among the strangest distinctions may well be its failure to adopt the metric system, making it the only industrialized country in the entire world to refuse to do so.
While this has led to some notable problems, including the loss of the US' Mars Climate Orbiter in 1997 after an engineering team used the metric system instead of the US' imperial system, it also has an effect on the US Food and Drug Administration (FDA). At present, regulators receive laboratory data in clinical trials as measured using US Conventional Units.
But as has been the case with several other forms of regulatory submissions over the last decade, FDA has said it's interested in harmonizing its data acceptance standards with thoseof other countries in an attempt to make it less onerous for companies to submit data.
"Since industry-sponsored clinical trials data is used globally, Système International (SI) units are the standard reporting mechanism," FDA wrote in an email to industry press. "The cost to industry to provide them in both units is very high, particularly if the request comes late in the development or review process."
However, unlike previous harmonization efforts, where FDA could create common forms with regulators from other countries to make it easier to submit documents, this harmonization effort is contingent largely upon the ability of its staff to understand the data it receives.
"[H]ealth care providers in the US are trained using US Conventional Units, and some lab results don't easily convert," FDA continued in its email. FDA said its drug and biologic evaluation units are currently evaluating where it could "identify a reasonable subset of lab tests that pose significant interpretation risks that should always be reported in both units."
It is further considering whether "standard conversion tools" could be used to help its staff review lab data more easily, it said.
"In the absence of a holistic transition within the U.S. healthcare community to SI units, conversion of certain lab test results to U.S. conventional units may be a necessary interim step toward a transition to full SI unit reporting," the agency wrote in an online statement.
In the meantime, sponsors should communicate and solicit input from review divisions on conversion needs as early in the regulatory process as possible. "[FDA] encourages sponsors to discuss this issue with FDA before the start of Phase 3 trials," it wrote. "In some cases the issue may warrant discussion with FDA at the End-of-Phase 2 meeting. If conversion requests are received, sponsors are advised to discuss the conversion request as early as possible with the review division and if needed, provide a proposal for what can be reasonably accomplished to meet the review division's needs without undue burden in time or costs."
Second FDA Statement