First Supplemental Indenture to 8.75% Senior Subordinated Notes Due 2012—Inverness Medical Innovations, Advantage Diagnostics, and U.S. Bank Trust

EXHIBIT 4.1

FIRST SUPPLEMENTAL INDENTURE

        THIS FIRST SUPPLEMENTAL INDENTURE, dated as of June 15, 2004 (this "First Supplemental Indenture"), to the Indenture (as defined below), among Inverness Medical Innovations, Inc., a Delaware corporation (the "Issuer"), the Guarantors (as defined in the Indenture), Advantage Diagnostics Corporation, a Delaware corporation (the "Additional Guarantor") and U.S. Bank Trust National Association, as Trustee (the "Trustee").

RECITALS

        WHEREAS, the Issuer has issued its 8³/4% Senior Subordinated Notes due 2012 (the "Notes") in the aggregate principal amount of $150,000,000 under and pursuant to the Indenture, dated as of February 10, 2004 (the "Indenture"), among the Issuer, the Guarantors listed therein and the Trustee.

        WHEREAS, unless the context requires otherwise, all capitalized terms used but not otherwise defined herein will have the meanings ascribed thereto in the Indenture.

        WHEREAS, the Additional Guarantor has become a Restricted Subsidiary and pursuant to Section 4.14 of the Indenture is entering into this First Supplemental Indenture to thereby become a Guarantor as provided in Article Eleven of the Indenture.

        WHEREAS, pursuant to Section 9.01(5) of the Indenture, the Issuer, the Guarantors, the Additional Guarantor and the Trustee may enter into this First Supplemental Indenture without the consent of any Holder.

AGREEMENT

        NOW, THEREFORE, for and in consideration of the premises and the mutual covenants and agreements hereinafter set forth, the parties hereto agree as follows:

ARTICLE I
ADDITIONAL GUARANTOR

        Section 1.01.    Additional Guarantor.    The Additional Guarantor hereby agrees, jointly and severally with all of the Guarantors, to unconditionally guarantee all of the Issuer's obligations under the Notes and the Indenture as a Guarantor thereunder on the terms and subject to the conditions set forth in the Indenture and to be bound by all provisions of the Indenture applicable to a Guarantor.

        Section 1.02.    First Supplemental Indenture.    This First Supplemental Indenture is supplemental to, and is entered into, in accordance with Section 9.01 of the Indenture, and except as modified, amended and supplemented by this First Supplemental Indenture, the provisions of the Indenture will remain in full force and effect.

ARTICLE II
MISCELLANEOUS

        Section 2.01.    Duplicates.    All parties may sign any number of copies of this First Supplemental Indenture. Each signed copy or counterpart shall be an original, but all of them together shall represent the same agreement.

        Section 2.02.    Successors and Assigns.    All agreements of the Issuer, the Guarantors and the Additional Guarantor in this First Supplemental Indenture shall bind their respective successors. All agreements of the Trustee in this First Supplemental Indenture shall bind its successor.

        Section 2.03.    Severability.    To the extent permitted by applicable law, in case any one or more of the provisions in this First Supplemental Indenture shall be held invalid, illegal or unenforceable, in any respect for any reason, the validity, legality and enforceability of any such provision in every other respect and of the remaining provisions shall not in any way be affected or impaired thereby, it being intended that all of the provisions hereof shall be enforceable to the full extent permitted by law.

        Section 2.04.    Governing Law.    This First Supplemental Indenture will be governed by and construed in accordance with the laws of the State of New York.

        IN WITNESS WHEREOF, the parties hereto have caused this Indenture to be duly executed all as of the date first written above.

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EXHIBIT 4.1