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                                                                   EXHIBIT 10.43

                                COMMERICAL LEASE

     THIS COMMERCIAL LEASE (the "Lease"), is made this 1st day of August, 1998,
between the Chang Family Trust ("Lessor"), and Applied Biotech, Inc., a
California corporation, with offices at 10237 Flanders Court, San Diego
California 92121 ("Lessee").

1.   LEASED PREMISES.

     Lessor hereby leases to Lessee and Lessee hereby leases from Lessor, upon
     and subject to the terms and provisions of this Lease, the premises
     described on Appendix A and located at 10237 Flanders Court, San Diego,
     California, together with all buildings and other improvements now or
     hereafter located thereon and all rights appurtenant thereto (the
     "Premises"). For the purposes of this Agreement, the parties hereby agree
     that the building on the Premises contains 40,000 square feet.

2.   TERM.

     Lessor demises the Premises for a term of five (5) years, commencing August
     1, 1998, and ending on July 31, 2003 (the "Term"), unless terminated
     earlier pursuant to the terms of this Lease.

3.   OPTION TO EXTEND TERM.

     Lessor grants to Lessee an option ("Option") to extend the Term for two (2)
     additional periods of five (5) years each, the first such extension
     commencing on August 1, 2003 and the second such extension commencing on
     August 1, 2008. If the Lessee exercises the Option, the additional term of
     five (5) years shall constitute part of the Term. To exercise the Option
     for the first extension, Lessee must give Lessor notice in writing at least
     sixty (60) days prior to August 1, 2003. To exercise the Option for the
     second extension, Lessee must give Lessor notice in writing at least sixty
     (60) days prior to August 1, 2008. All terms and conditions of this Lease
     shall continue to apply during the term of the Option.

4.   RENT.

     Commencing on August 1, 1998 and continuing throughout the initial five (5)
     year Term, Lessee shall pay to Lessor an annual base rent equal to four
     hundred forty thousand dollars ($440,000) ("Annual Base Rent"), payable in
     equal monthly installments of thirty six thousand, six hundred sixty-six
     dollars and sixty-six cents ($36,666.66) in advance on the first business
     day of each month for that month's rental. If Lessee exercises its Options
     to extend the Term, (i) the Annual Base Rent for the first five (5) year
     extension shall be four hundred eighty thousand dollars ($480,000), payable
     in equal monthly installments of forty thousand dollars ($40,000) in
     advance on the first business day of each month for that month's rental,
     and (ii) the Annual Base Rent for the second five (5) year extension shall
     be five hundred twenty thousand dollars ($520,000), payable in equal
     monthly installments

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     of forty three thousand three hundred thirty-three dollars and thirty-three
     cents ($43,333.33) in advance on the first business day of each month for
     that month's rental. All Annual Base Rent payments shall be made to Lessor,
     at the address specified above or any address as specified in writing by
     Lessor. The amount of monthly installments payable by Lessor shall be
     prorated for any partial month of the Term.

5.   TAXES/ASSESSMENTS/UTILITIES

     5.1       As additional rent, the Lessee shall pay when due all real
               property taxes and other assessments (hereinafter the "Taxes and
               Assessments"), of every nature and description, whether general
               or special, (including, without being limited to, taxes and other
               assessments of water, sewer, fire or other special district)
               levied or assessed against the Premises during the Term;
               provided, however, that Lessee shall be entitled to elect to pay
               by installment payments any Taxes and Assessments and provided
               further that any Taxes and Assessments which apply for periods
               not concurrent with the Term shall be prorated so that Lessee
               pays only that portion which accrues or accrued during the Term.

     5.2       Taxes and Assessments payable hereunder for the calendar year in
               which this Lease commences or terminates will be prorated on the
               basis of a 365 day year, the Lessee paying the Taxes and
               Assessments assessed as of the December 31 immediately preceding
               the calendar year in which this Lease commences or terminates in
               proportion to that part of the calendar year during which the
               Lessee has possession of the Premises. If this Lease terminates
               prior to the time when the amount of the Taxes and Assessments
               payable for the calendar year in which termination occurs are
               known, appropriate provision for their adjustment will be made.

     5.3       The Lessee will furnish to Lessor evidence of the payment of the
               Taxes and Assessments within 10 days following the date upon
               which the payment is due.

     5.4       The Lessee shall have the right to contest the amount or validity
               of any Tax and Assessment by appropriate proceedings but only
               after payment of such Tax and Assessment unless such payment
               would bar such contest.

     5.5       Lessee shall pay all utilities with respect to the Premises,
               including but not limited to water, sewer, heat, gas, oil and
               electricity, and all services with respect to the Premises and
               the entranceways, exit ways and driveways providing access to the
               Premises, including, but not limited to, maintenance and
               cleaning, landscaping and snow removal.

6.   CARE AND MAINTENANCE OF PREMISES.

     Except as set forth in Section 15 hereof, Lessee shall, at its own expense,
     keep and maintain the Premises in good and safe condition and repair,
     reasonable wear and tear excepted, including roof, exterior walls,
     structural foundations, plate glass, electrical

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     wiring, plumbing and heating installations and any other system or
     equipment upon the Premises.

7.   ALTERATIONS AND IMPROVEMENTS.

     Lessee may make any non-structural alterations and improvements to the
     Premises which do not (a) materially or adversely affect the improvements
     on the Premises, (b) injure the structural safety of the buildings on the
     Premises, or (c) materially impair the value of the Premises or the
     building on the Premises. Any structural alterations and improvements to
     the Premises shall be subject to the Lessor's prior approval, which
     approval shall not be unreasonably withheld, conditioned or delayed.

8.   LESSEE'S TRADE FIXTURES.

     For the purposes of this Agreement, the term "Lessee's Trade Fixtures"
     means all machinery, equipment and other items of personal property owned
     by the Lessee and especially designed or fitted for use in its trade or
     business which are not affixed or incorporated into the buildings in such a
     manner that their removal will cause substantial damage to the structure of
     the building. It is understood that Lessee may install Lessee's Trade
     Fixtures in the building on the Premises. All Lessee's Trade Fixtures will,
     notwithstanding the manner of their installation, remain the property of
     the Lessee and will be removed by the Lessee upon the termination of this
     Lease. The Lessee will repair any damage to the Premises occasioned by the
     removal of Lessee's Trade Fixtures.

9.   ORDINANCES AND STATUTES.

     Lessee shall comply with all statutes, ordinances and requirements of all
     municipal, state and federal authorities now in force, or which may
     hereafter be in force, pertaining to the Premises, occasioned by or
     affecting the use thereof by Lessee.

10.  ASSIGNMENT AND SUBLETTING.

     Lessee shall not assign this Lease or sublet any portion of the Premises
     without prior written consent of the Lessor, which consent shall not be
     unreasonably withheld or delayed. Notwithstanding the foregoing, Lessee
     may, without the prior consent of Lessor, assign this Lease or sublet all
     or a portion of the Premises to a parent, subsidiary, or entity under
     common control with Lessee, or to any party who acquires all or
     substantially all of the assets of Lessee, whether by way of merger,
     consolidation, reorganization or sale.

11.  ENTRY AND INSPECTION.

     Lessee shall permit Lessor or Lessor's agents to enter upon the Premises at
     reasonable times and upon reasonable notice, for the purposes of inspecting
     the same. Lessee will permit Lessor at any time within sixty (60) days
     prior to the expiration of this Lease to place upon the Premises any usual
     "To Let" or "For Lease" signs, and permit persons desiring to lease the
     same to inspect the Premises thereafter.

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12.  INDEMNIFICATION.

     12.1      Lessee shall hold harmless, indemnify and defend Lessor and its
               employees and agents from all liability, penalties, losses,
               damages, costs, expenses, causes of action, claims and/or
               judgments (collectively "Losses") arising by reason of any death,
               bodily injury, personal injury or property damage to the extent
               resulting from the negligent act or omission of Lessee, its
               agents, contractors, or employees, a breach by Lessee of this
               Lease, or a violation by Lessee of any law.

     12.2      Lessor shall hold harmless, indemnify and defend Lessee and its
               employees and agents from all Losses arising by reason of any
               death, bodily injury, personal injury or property damage to the
               extent resulting from the negligent act or omission of Lessor,
               its agents, contractors, or employees, a breach by Lessor of this
               Lease, or a violation by Lessor of any law.

13.  INSURANCE.

     13.1      The Lessee, at its expense, shall maintain public liability
               insurance in the amount of $1,000,000 for bodily injury or death
               in any one accident and $1,000,000 per occurrence for property
               damage relating or claimed to relate to the Premises The Lessee
               shall maintain insurance on the buildings on the Premises for the
               benefit of the Lessor, any mortgagee of the Lessor, and the
               Lessee (as their interests may appear) against loss or damage by
               fire or other risks now embraced by standard "all risks of loss"
               coverage, so-called, in an amount not less than one hundred
               percent (100%) of the then full replacement cost of the
               buildings. The Lessee shall also purchase boiler and machinery
               insurance insuring the Lessor and the Lessee.

     13.2      Lessee shall provide Lessor with a Certificate of Insurance
               showing Lessor as Additional Insured - Lessor on the public
               liability insurance referenced in Section 13.1. The Certificate
               shall provide for a ten-day written notice to Lessor in the event
               of cancellation or material change of coverage. To the maximum
               extent permitted by insurance policies that may be owned by
               Lessor or Lessee, Lessee and Lessor, for the benefit of each
               other, waive any and all rights of subrogation that might
               otherwise exist.

14.  EMINENT DOMAIN.

     If the Premises or any part thereof are taken in condemnation proceedings
     or by exercise of any right of eminent domain, (i) the Lessor will be
     entitled to collect from the condemnor the entire award that may be made in
     such proceeding without deduction therefrom for any interest of the Lessee
     under this Lease except that the Lessee shall be entitled to file a claim
     and/or bring a separate action for the value of that portion of the
     Lessee's Trade Fixtures and improvements which were taken and the cost of
     relation of Lessee; and (ii) this Lease will terminate on the date of such
     taking and the Annual Base Rent and all other

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     payments required to be made by the Lessee hereunder will be apportioned
     and paid to the date of such taking.

15.  DESTRUCTION OF PREMISES.

     In the event that all or a portion of the Premises or the building on the
     Premises are damaged by fire or other peril or casualty, and such
     restoration, repair or rehabilitation can be made within thirty (30) days
     of the date of such damage, then Lessor shall immediately proceed with all
     due diligence to restore, repair or rehabilitate the Premises and/or
     building to its condition prior to such loss. Lessor shall have the right
     to all applicable insurance for the purpose of making any such restoration,
     repairs or rehabilitation, and the amount recovered from such insurance
     shall be held in trust by Lessor and solely used to pay the costs for such
     restoration, repair or rehabilitation. During the period of restoration,
     repair or rehabilitation, the Annual Base Rent shall be equitably adjusted
     (based on the square footage area suitable for Lessee's use and occupancy,
     if any) until the entire Premises and building are suitable, in Lessee's
     reasonable judgment, for Lessee's use and occupancy. In the event the
     damage cannot be repaired within thirty (30) days after the date of such
     damage, either party may, at any time thereafter, elect by written notice
     to the other to terminate this Lease as of the date of the damage. In case
     of damage contemplated under this section, the Lessor shall, within ten
     (10) days of the loss, advise Lessee of the following: (i) estimated cost
     of restoration, repair and rehabilitation; (ii) proposed commencement date
     for making the restoration and repairs; and (iii) date by which the
     restoration, repairs and rehabilitation will be completed. In the event
     this Lease is not terminated pursuant to the above, all Annual Base Rent
     shall abate on a daily basis during the period that the Premises are not
     suitable for Lessee's use and occupancy. Lessor shall complete such repairs
     as promptly as possible. A total destruction of any of the buildings
     situated on which the Premises shall terminate this Lease.

16.  LESSOR'S REMEDIES ON DEFAULT.

     The Lessee will be in default under this Lease upon the occurrence of any
     of the following events or conditions as to the Lessee; (i) the Lessee's
     failure to pay the Annual Base Rent or make the other payments at the times
     and in the manner provided for herein, such failure having continued for a
     period of 10 days after written notice from Lessor; (ii) the Lessee's
     failure to perform or fulfill any other term, condition or agreement
     contained or referred to herein, on the part of the Lessee to be performed
     or fulfilled, such failure having continued, in the absence of reasonable
     efforts having been made by Lessee to correct the same, for a period of
     thirty (30) days after written notice thereof shall have been given by the
     Lessor to the Lessee, provided that if such failure to perform or fulfills
     such term, condition or agreement cannot reasonably be remedied within
     thirty (30) days, within such further time as may be reasonably necessary,
     with due diligence, to complete such performance; (iii) proceedings in
     bankruptcy or for liquidation, reorganization, or rearrangement of the
     Lessee's affairs shall be instituted by or against the Lessee, and such
     proceedings shall not be dismissed within 60 days of their filing; (iv) a
     receiver or trustee shall be appointed for all or substantially all of
     Lessee's business or assets on the grounds of Lessee's insolvency; (v) the
     Lessee shall make an assignment for the benefit of its creditors.

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17.  QUIET ENJOYMENT.

     Upon paying the rent and all other payments required to be made by the
     Lessee hereunder, and upon the Lessee performing and fulfilling all terms,
     conditions or agreements on the Lessee's part to be performed and
     fulfilled, the Lessee will quietly have and enjoy the Premises during the
     Term without hindrance by any person claiming by, through or under the
     Lessor.

18.  NOTICES.

     Any notice which either party may, or is required to give to the other
     party under this Lease shall be given by facsimile transmission, overnight
     courier, or certified or registered mail, postage prepaid, properly
     addressed to the respective parties as follows:

     If to Lessee:               Diagnostic Reagents, Inc.
                                 Attn.:  Dr. Yuh-geng Tsay
                                 601 California Avenue
                                 Sunnyvale, California  94086

     With a copy to:             Sybron Laboratory Products Corporation
                                 Attn.:  Michael K. Bresson, Esq.
                                 48 Congress Street
                                 Portsmouth, New Hampshire  03801

     If to Lessor:               Shung-Ho Chang Family Trust
                                 Attn.:

     Or to such other addresses as either party may from time to time by written
     notice designate as its address for the purposes of this Agreement and
     shall be deemed to have been received on the day following dispatch of any
     facsimile transmission sent after 5:00 PM EST, the day of receipt from any
     courier, and the fourth day following the mailing of any letter.

19.  GOVERNING LAW.

     This Lease and the performance thereof will be governed, interpreted,
     construed and regulated in accordance with the laws of the State of
     California, without regard to any conflicts of laws.

20.  SUBORDINATION.

     This Lease is and shall be subordinated to all existing and future liens
     and encumbrances against the property.

21.  ENTIRE AGREEMENT.

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     The foregoing supercedes any and all other agreements, either oral or in
     writing, between the parties, and constitutes the entire agreement between
     the parties with respect to its subject matter. Each party acknowledges and
     represents that no representations, inducements, promises or agreements,
     orally or otherwise, have been made by any party, or any person acting on
     behalf of any party, which are not embodied in this Agreement, and that no
     other agreement or statements of promise not contained in this Agreement
     shall be valid or binding. This Agreement may not be altered, amended or
     modified except by written instrument signed by both parties.

22.  ORDINANCES AND STATUTES.

     Lessee shall copy with all statutes, ordinances and requirements of all
     municipal, state and federal authorities now in force, or which may
     hereafter by in force, pertaining to the Premises, occasioned by or
     affecting the use thereof by Lessee.

     IN WITNESS WHEREOF, and intending to be legally bound, the parties have
signed this Agreement below.


LESSOR                                    LESSEE

CHANG FAMILY TRUST                        APPLIED BIOTECH, INC.


By:    /s/ Shung-Ho Chang                 By:  /s/ Yuh-geng Tsay
   -----------------------------------       ---------------------------------

Name:   Shung-Ho Chang                    Name:  Yuh-geng Tsay
     ---------------------------------         -------------------------------

Title:  Trustee                           Title: President of DRI
      --------------------------------         -------------------------------