<PAGE>

                                                                    EXHIBIT 10.5

                     FIRST AMENDMENT TO SETTLEMENT AGREEMENT

         THIS FIRST AMENDMENT TO SETTLEMENT AGREEMENT ("First Amendment"),
effective as of October 1, 2003, is made by and among Applera Corporation, a
Delaware corporation, acting through its Applied Biosystems Group ("AB"), Irena
Bronstein, of Newton, Massachusetts ("Bronstein"), Lumigen, Inc., a Michigan
corporation ("Lumigen"), A. Paul Schaap, of Grosse Point Park, Michigan
("Schaap"), Wayne State University, a not for profit constitutional body
corporate organized under the laws of the State of Michigan ("WSU"), and
Diagnostic Products Corporation, a California corporation, ("DPC");

         WHEREAS, Bronstein, Lumigen, Schaap, and WSU, along with Tropix, Inc.,
a Delaware corporation ("Tropix"), entered into a Settlement Agreement made
effective as of February 10, 1995 ("the Settlement Agreement"); and

         WHEREAS, Tropix was later acquired by and thereafter merged into AB
(f/k/a The Perkin-Elmer Corporation) and currently operates through Applera's
Applied Biosystems Group; and

         WHEREAS, DPC purchases PPD and TB Enhancer (both as defined in the
Settlement Agreement) from Lumigen; and

         WHEREAS, AB, Bronstein, Lumigen, Schaap and WSU, wish to amend the
Settlement Agreement as set forth in this First Amendment, and DPC, a guarantor
of Lumigen's payments to Tropix under the Settlement Agreement, wishes to be a
party to this First Amendment and to be bound by the covenants expressly set
forth herein;

         NOW, THEREFORE, in consideration of the mutual undertakings set forth
herein, the parties agree as follows:

         1. Unless the context of this First Amendment indicates otherwise,
capitalized terms used herein shall have the same meaning as defined in the
Settlement Agreement.

         2. AB covenants and agrees, on its own behalf, and on behalf of its
affiliates, parent and subsidiary corporations, predecessors (specifically
including Tropix), successors and assigns, not to institute any suit, action or
proceeding in any court, state or federal, U.S. or foreign, or in any patent
office or tribunal, against Lumigen, or DPC, or any of their suppliers,
customers, licensees, affiliates, subsidiary or parent corporations,
predecessors, successors or assigns, arising out of DPC's use or sale or its
customers' use or sale of TB Enhancer purchased by DPC from Lumigen in
conjunction with PPD purchased by DPC from Lumigen as an element of human in
vitro diagnostics or veterinary diagnostics. DPC is no longer required to
purchase from AB, DPC's requirements for PPD and TB Enhancer for veterinary
diagnostic immunoassays.
<PAGE>
         3. DPC agrees to pay to AB within thirty (30) days after the end of
each calendar quarter starting January 1, 2003 and ending upon the last to
expire of the Assigned Patent Rights, as defined in the Settlement Agreement, a
royalty equal to * % of DPC's sales of Kits of medical diagnostic and veterinary
reagents which are used in conjunction with PPD and TB Enhancer. The term Kit
shall mean and include any product or commercial test which is manufactured by
or on behalf of DPC and sold or otherwise commercially exploited by or on behalf
of DPC and delivered for use with PPD and TB Enhancer as an element of human in
vitro diagnostics or veterinary diagnostics. A Kit normally contains active
buffers, antibody/antigen/DNA/peptide, conjugate and substrate (PPD and
enhancers). As a basis for determining the royalty rate set forth above, DPC has
provided its applicable reagent sales during calendar years 2000, 2001, and 2002
(see Exhibit 1).

         4. Lumigen's obligation under Section 5.1 of the Settlement Agreement
to pay to AB a royalty equal to * percent ( * %) of Gross Revenues shall
continue; provided, however, that Lumigen shall exclude Gross Revenue derived
from the business of Lumigen with DPC as described in paragraph 2 above. This
exclusion shall continue in effect so long as DPC shall make the payments called
for in paragraph 3 above.

         5. Except as modified by the provisions of this First Amendment, all
terms contained in the Settlement Agreement shall continue in full force and
effect.

         IN WITNESS WHEREOF, the parties have caused this First Amendment to be
executed, corporate parties acting by and through their duly-authorized
officers, all on the day and date first above written.

                                          Applera Corporation
                                          through its Applied Biosystems Group

                                          By     /S/ Laura Lauman
                                             -----------------------------------
                                          Its      Vice President
                                             -----------------------------------

* Omitted pursuant to a request for
confidential treatment.  This material has         /S/ Irena Bronstein
been filed separately with the SEC.             --------------------------------
                                                Irena Bronstein


                                                Lumigen, Inc.


                                                 By      /S/ Gary T. Priestap
                                                   -----------------------------
                                                     Its  Vice President
                                                        ------------------------


                                       2
<PAGE>
                                                   /S/ A. Paul Schaap
                                                --------------------------------
                                                A. Paul Schaap

                                                Wayne State University


                                                By       /S/
                                                   -----------------------------
                                                     Its  Vice President/General
                                                          Counsel
                                                        ------------------------

                                                Diagnostic Products Corporation


                                                By       /S/ Michael Ziering
                                                   -----------------------------
                                                     Its  President
                                                        ------------------------


                                       3
<PAGE>
                                    EXHIBIT 1

              Lumigen Revenue with Diagnostic Products Corporation

                                November 7, 2002


<TABLE>
<CAPTION>
                       Total Lumigen           *% Royalty               DPC             *% Royalty
                          Revenue            paid to Tropix           Reagent          as a % of DPC
Year                      with DPC         from DPC business           Sales           Reagent Sales
----                      --------         -----------------           -----           -------------
<S>                    <C>                 <C>                      <C>                <C>
2000                         *                     *                 89,910,027             *%

2001                         *                     *                117,772,135             *%

2002 (est)                   *                     *                144,734,132             *%

2003 (projection)            *                     *                161,525,000             *%

4 year total                                       *                513,941,294             *%
</TABLE>



     * Omitted pursuant to a request for confidential
     treatment.  This material has been filed
     separately with the SEC
<PAGE>
                           CERTAIN DEFINITIONS USED IN
                     FIRST AMENDMENT TO SETTLEMENT AGREEMENT

         "PPD" shall mean 4-methoxy-4-(3-phosphatephenyl)spiro[1,2-dioxetane-3,
2-adamantane]disodium salt.

         "TB Enhancer" shall mean polyvinylbenzyltributylphosphonium chloride.

         "Assigned Patent Rights" shall mean the patents and patent applications
identified on Exhibit A attached hereto and any patents issuing from any such
patent applications, and any continuations, divisions, substitutions, reissues,
extensions and renewals of any of the foregoing.
<PAGE>
                                    EXHIBIT A

                             ASSIGNED PATENT RIGHTS

                                  U.S. PATENTS

                                    4,962,192
                                    4,959,182
                                    5,004,565
                                    5,386,017

                                U.S. APPLICATIONS

                                   06/887,139
                                   07/023,649
                                   07/265,890
                                   07/677,097
                                   08/020,302
                                   08/021,022
                                   08/186,461
                                   08/262,564
                                   08/339,085

                                 FOREIGN PATENTS

<TABLE>
<CAPTION>
                     Country                         Patent No.
                     -------                         ----------
<S>                 <C>                              <C>
                    Australia                          603,736
                      Korea                            69,259
                     Taiwan                            46,563
</TABLE>
<PAGE>
                           FOREIGN PATENT APPLICATIONS

<TABLE>
<CAPTION>
              Country                     Filing Date                           Serial No.
              -------                     -----------                           ----------
<S>                                       <C>                                   <C>
               Canada                        5/13/87                             537,003-5
               Canada                        9/21/93                             616,729-2
               Canada                        5/31/89                             601,376-7
               Canada                       12/20/89                             2,006,222

                Japan                        6/11/91                            236,758/91
                Japan                        6/11/91                            236,759/91
                Japan                        7/24/89                            191,247/89
                Japan                        6/29/93                            187,042/93
                Japan                       12/21/89                            502,424/89
                 *EPO                        6/23/87                            87108978.5
                 *EPO                       11/25/93                            93119049.0
                 *EPO                        7/24/89                            92109406.6
                 *EPO                        8/21/92                            92114339.2
                 *EPO                        7/24/89                            89113627.7
                 *EPO                       12/21/89                            89123690/3
                China                        7/27/89                            89106249.1
                China                        7/27/89                            93120975.7
                India                         9/6/89                            454/MAS/89
                India                         7/6/93                            457/MAS/93
</TABLE>


* Includes (1) any national applications filed on the basis of this application,
(2) all rights to file any national application in any state designated in this
application, and (3) all national and European patents issued and to issue based
on this application.