To the Editor.—Lo and Alter1 and Beste et al2,3 have highlighted the importance of ensuring commutability of materials used for interinstrument comparisons. Laboratories that are College of American Pathologists (CAP) accredited will be familiar with the need to demonstrate comparability of instruments and methods described in the Common Checklist item COM.04250.4 This requirement states a preference to use patient specimens to avoid the matrix effects discussed by Lo and Alter1 but does allow quality control materials to be used for tests when the same instrument platform with both control material and reagents of the same manufacturer and lot number is in use. Such an approach would not necessarily detect all conceivable analytical differences between platforms, and patient samples would be the material of choice.
This checklist item is not applicable for laboratories with different CAP numbers and is relevant only to laboratories with multiple analytical platforms or whose satellite or “sister” laboratories share the same CAP number. The need to demonstrate similar comparability between independent laboratories displaying results in a common electronic medical record system is arguably outside the scope of this requirement. With the rise of regional and national electronic medical record systems, there is a pressing need for equivalent requirements on the agreement needed between institutions sharing a common electronic test repository and result interface to allow interoperability of numeric results. These should explicitly discuss the requirements that allow the use of common reference intervals and trending across institutions.5 For the CAP Accreditation Program, this could be covered within the computer section of the General Checklist or by revision and expansion of the existing Common Checklist item COM.04250 described above.4,6
The author has no relevant financial interest in the products or companies described in this article.