<PAGE>

                                 EXHIBIT 10.23

February 6, 2001

Dickerson Wright
Chairman and Chief Executive Officer
U.S. Laboratories, Inc.
7895 Convoy Court, Suite 18
San Diego, CA  92111

     Re:  Investor Relations Agreement

Dear Dick:

This letter agreement contains the terms under which Pont Loma Partners, Inc.
("PLP") will provide services to U.S. Laboratories, Inc. ("USLB").  It is a
contract between PLP and USLB.  PLP and USLB will be referred to as a "Party" or
collectively, as the "Parties."  The relationship between the Parties is that of
independent contractor and nothing else.

1.  Services: USLB retains PLP to provide financial advisory and investor
    relations services. Among other duties, PLP shall introduce USLB to its
    contacts in the financial community and advise USLB on expanding its network
    of securities firms, stockbrokers, market makers, research analysts, and
    institutional and individual shareholders.

2.  Access to Information: USLB acknowledges that in order for PLP to
    successfully complete any aspect of this project, it must fully cooperate
    with PLP. On execution of this agreement, USLB agrees to promptly provide
    PLP with copies or make available the originals of all requested
    information. PLP agrees to keep all such information confidential until such
    time that USLB is authorized to release such information or required to do
    so by court of law.

3.  Confidentiality: The Parties may furnish each other confidential
    information. "Confidential Information" means all non-public business and
    technological information. Confidential Information does not include
    information that is public at the date of disclosure, information that is
    legally disclosed by a third party who is under no duty not to disclose the
    information, and information a Party knew before the disclosing Party
    disclosed that information publicly or directly to the receiving Party and
    provided the receiving party did not obtain that information illegally. The
    Parties agree to keep all Confidential Information confidential until it is
    no longer Confidential Information. The Parties agree to maintain the
    Confidential Information in strict confidence, not disclose it to any third
    party unless required in connection with obligations under this agreement.
    The Parties will require their officers, directors, employees, agents and
    representatives to similarly restrict disclosure and use. The Parties are
    responsible for any wrongful disclosure by its employees, officers,
    directors and agents. If any court
<PAGE>

Investor Relations Agreement
February 6, 2001
Page 2 of 4

    or other authority orders disclosure of Confidential Information, the
    Parties will use their best efforts to protect confidentiality and
    immediately notify the disclosing Party so that it may also take actions to
    preserve confidentiality.

4.  Expenses: USLB agrees to reimburse PLP for all reasonable out-of-pocket
    expenses. PLP will periodically bill USLB for all expenses as they are
    incurred. PLP agrees that any single expense of $500.00 or more will require
    advance approval from USLB before the expense is incurred.

5.  Non-Circumvention: USLB agrees that all information relating to potential
    business opportunities identified by PLP and the contacts identified by PLP
    relating to such opportunities are Confidential Information and will not be
    shared by USLB with any other party without advance written consent of PLP.
    The Parties agree that any transaction with any such contact without the
    participation of PLP before or after termination of this Letter Agreement
    must include competitive compensation for PLP.

6.  Cash Compensation: USLB will pay to PLP $3,000 per month in advance.
    Payments shall be due on the 15th of each month. This Agreement will
    commence and the first payment will be due on February 15, 2001.

7.  Equity Compensation:  USLB will grant the following stock purchase warrants
    to PLP per the following terms:

    a.  $40,000 common stock purchase warrants with a strike price of $4.50 to
        be granted immediately upon the execution of this Agreement.

    b.  40,000 common stock purchase warrants with a strike price of $4.50 to be
        granted immediately, yet exercisable only if the closing bid price of
        USLB exceeds $6.00 for 20 consecutive trading days.

    c.  40,000 common stock purchase warrants with a strike price of $4.50 to be
        granted immediately, yet exercisable only if the closing bid price of
        USLB exceeds $8.00 for 20 consecutive trading days.

    d.  The above stock purchase warrants will expire three (3) years from the
        date they are granted.

8.  Term of Engagement:  The term of this Agreement shall be one (1) year and
    will commence on February 15, 2001.

9.  Limitation of Liability: Neither PLP, nor its affiliates, licensors,
    contractors, representatives or agents will be liable to USLB for any
    indirect, incidental, special, consequential, exemplary or punitive damages
    arising from, connected with or relating to this letter agreement. This
    include any lost profits or revenues, lost savings, or other similar
    damages. Under no circumstances will PLP's liability ever exceed the amount
    paid to it by USLB excluding expense reimbursement. Each party recognizes
    and agrees that the warranty disclaimers and liability and remedy
    limitations in this

                                      2

<PAGE>

Investor Relations Agreement
February 6, 2001
Page 3 of 4


    agreement are material bargained for terms of this agreement. They take into
    account and reflect the consideration given by each party pursuant to this
    agreement and the decision by each party to enter into this agreement.

10. Arbitration: The Parties agree to resolve all claims, dispute and
    controversies past, present or future arising out of or related to, this
    letter agreement against each and against respective officers, directors,
    agents and employees in final and binding arbitration in San Diego,
    California under the rules of the American Arbitration Association ("AAA").
    The Parties agree to waive any rights to trial by jury, adjudication in a
    different venue and notice requirements. The arbitrator will be an
    individual knowledgeable about the subject matter of the dispute mutually
    agreed upon by the Parties from a AAA panel. If the Parties cannot agree on
    an arbitrator, each Party will select an individual from the AAA list, and
    the two so selected will choose the arbitrator from another AAA panel. The
    arbitrator will apply the substantive law of California without regard to
    the principles of conflicts of law or U.S. law, as applicable. The
    arbitrator will have the exclusive authority to resolve disputes relating to
    interpretation, applicability and enforcement of this letter agreement. Each
    Party agrees to split the cost of arbitration excluding legal fees. The
    arbitration process, including selection of the arbitrator, exchange of
    requests for information and the arbitration hearing will be completed
    within 60 days following the institution of the arbitration by a party, and
    the actual arbitration hearing shall be limited to 1 day. The parties may
    enter judgment on any arbitration award in any court having jurisdiction.
    This paragraph shall survive termination of this agreement. Both arbitrators
    and courts of law shall award all costs (excluding arbitration costs) and
    reasonable attorney fees to the prevailing party in any arbitration or
    litigation.

11. No Waiver: The Parties will not treat any failure to object to any terms of
    this agreement as a waiver of those terms. Consent or approval on any one
    occasion does not mean consent on any other item or any other time.

12. Governing Law: This letter agreement shall be interpreted equally as to all
    Parties. It will be governed by the laws of the State of California without
    giving effect to choice of law provisions.

13. Severability: If an arbitrator or court of competent jurisdiction determines
    any part of this agreement invalid or unenforceable, and the decision is not
    subject to appeal, the Parties agree that the particular part will be deemed
    severed. If a term is invalid because of its scope, the term will be deemed
    valid to the extent of the scope permitted by applicable law. This letter
    agreement will be binding on successors and assigns.

14. Notification: Should a Party have to notify the other for any reason that
    Party agrees to do so in writing delivered personally, by mail or by
    reputable overnight delivery service. Notification shall be delivered to the
    following addresses:

                                       3
<PAGE>

Investor Relations Agreement
February 6, 2001
Page 4 of 4

          If to PLP:   Jeffrey J. Janda, Chief Executive Officer
                       Point Loma Partners, Inc.
                       701 B. Street, Ste. 1400
                       San Diego, California 92101

          If to USLB:  Dickerson Wright
                       Chairman and Chief Executive Officer
                       U.S. Laboratories, Inc.
                       7895 Convoy Court, Suite 18
                       San Diego, CA 92111

          The Parties can change these addresses by notifying each other in
          writing in accordance with the terms of this agreement.

If USLB wishes to be a Party to this letter agreement, and be bound by its
terms, please have an authorized representative on the approval page (signature
line provided below).  USLB should return a signed copy of this Agreement to PLP
together with a check in the amount of $3,000.00.

Sincerely,

/s/ Jeffrey J. Janda

Jeffrey J. Janda
Chief Executive Officer
Point Loma Partners, Inc.


ACKNOWLEDGEMENT AND APPROVAL:

We have read this five (5) page letter agreement.  We understand and accept its
contents.  We, the undersigned, also represent that we are authorized to sign on
behalf of our respective Parties and authorized to bind our respective Parties
to the provisions of this letter agreement.

Point Loma Partners, Inc.                      U.S. Laboratories, Inc.

By:  /s/ Jeffrey J. Janda                      By:  /s/ Dickerson Wright
   ---------------------------                         ------------------------
Name:  Jeffrey J. Janda                        Name:  Dickerson Wright

Title:  Chief Executive Officer                Title:  Chief Executive Officer

Date:  February 15, 2001                       Date:  February 15, 2001

                                       4
<PAGE>

                           POINT LOMA PARTNERS, INC.
                           701 B Street, Suite 1400
                             San Diego, CA  92101
                                (619) 233-0726



February 9, 2001

Dickerson Wright
Chairman and Chief Executive Officer
U.S. Laboratories, Inc.
7895 Convoy Court, Suite 18
San Diego, CA  92111

     Re:  Amendment to Investor Relations Agreement ("Amendment")

Dear Dick,

With respect to our Letter Agreement re: Investor Relations Agreement (the
"Original Agreement"), we have agreed to amend the Original Agreement as
follows:

1)  We hereby confirm that the date of the Original Agreement shall be as of
    February 6, 2001, the date on the first page of the Original Agreement.

2)  Section 5 of the Original Agreement, "Non-Circumvention," is hereby amended
    to read in its entirety:

               "Non-Circumvention:  USLB agrees that all information relating to
               potential business opportunities identified by PLP and the
               contacts identified by PLP relating to such opportunities are
               Confidential Information and will not be shared by USLB with any
               other party without advance written consent of PLP.  The Parties
               agree that any transaction before or after termination of this
               Letter Agreement with any such contact without the participation
               of PLP must include competitive compensation for PLP."

3)  Section 8 of the Original Agreement, "Term of Engagement", is hereby amended
    to read in its entirety: "The term of this Agreement shall commence on
    February 6, 2001 and end on February 9, 2003."
<PAGE>

IR Agreement Amendment
Februray 9, 2001
Page 2 of 3

4)  The equity compensation described in Section 7 of the Original Agreement
    shall be deleted in its entirety, and replaced by Sections 4, 5 and 6 of
    this Amendment.

5)  A warrant to purchase 65,000 shares of common stock at $4.50 per share,
    shall be granted and fully vested as of the date hereof. This warrant shall
    expire on February 8, 2004. U.S. Laboratories, Inc. ("USLB") hereby agrees
    to register the shares underlying this warrant in its upcoming registration
    statement.

6)  A second warrant to purchase 30,000 shares of common stock at $4.50 per
    share shall be granted by USLB to Point Loma Partners, Inc. ("PLP") on
    February 9, 2002 at the sole discretion of USLB if it deems that PLP has
    faithfully performed its duties. If so granted, this warrant shall expire on
    February 8, 2005. If so granted, USLB hereby agrees to include the shares
    issuable upon exercise of this warrant in any registration statement filed
    after February 9, 2002.

7)  A third warrant to purchase 25,000 shares of common stock at $7.00 per share
    shall be granted by USLB to PLP on February 8, 2003 at the sole discretion
    of USLB if it deems that PLP has faithfully performed its duties. If so
    granted, this warrant shall expire on February 7, 2006. If so granted, USLB
    hereby agrees to include the shares issuable upon exercise of this warrant
    in any registration statement filed after February 8, 2003.

8)  If PLP terminates or otherwise materially defaults under the Original
    Agreement, as amended by the terms of this Amendment (as may be further
    amended, the "Agreement") for any reason, then 50% of the cash payments
    received through the date of such termination shall be refunded promptly to
    USLB.

9)  Both parties acknowledge that the Original Agreement was in error,
    necessitating the changes set forth in this Agreement.

10) The Original Agreement shall remain in effect except as modified by the
    terms of this Amendment.

11) The parties represent to each other that the person signing below is
    authorized to sign on behalf of the respective parties to this Amendment and
    is authorized to bind such party to the provisions of this Amendment.

12) PLP hereby represents that (i) it is an accredited investor as such term is
    defined in Rule 501 promulgated under the Securities Act of 1933, as
    amended, and (ii) it is acquiring the warrant granted as of the date hereof
    for investment purposes only and not with a view towards resale or
    distribution.
<PAGE>

IR Agreement Amendment
Februray 9, 2001
Page 3 of 3

13) Each warrant granted pursuant to Section 4, 5 or 6 of this Letter Agreement
    shall be in substantially the same form as that certain Common Stock
    Purchase Warrant between USLB and Miller Capital Corporation, dated March
    15, 1998. Any such Warrant Agreement shall supersede any conflicting
    provision in the Agreement.

14) The parties may not assign their rights or obligations under the Agreement
    without the written counsel of the other party.

If you understand the above and it is acceptable to you, please sign the
attached acknowledgement where indicated and return a copy of this letter to me.

Thank you.

Sincerely,

/S/ JEFFREY J. JANDA

Jeffrey J. Janda
Chief Executive Officer
Point Loma Partners, Inc.


ACKNOWLEDGEMENT AND APPROVAL:


IN WITNESS WHEREOF, the undersigned have executed this Amendment as of the 9th
day of February, 2001.

Point Loma Partners, Inc.                     U.S. Laboratories, Inc.

/S/ JEFFREY J. JANDA                          /S/ DICKERSON WRIGHT

Name:  Jeffrey J. Janda                       Name:  Dickerson Wright

Title:  Chief Executive Officer               Title:  Chief Executive Officer