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                                                                 EXHIBIT 10.48

                                    GUARANTY


          THIS GUARANTY ("GUARANTY") IS MADE AS OF THIS 30TH DAY OF SEPTEMBER,
1998, BY CHIH PING LIU ("GUARANTOR") FOR THE BENEFIT OF CALYPTE BIOMEDICAL
CORPORATION, A DELAWARE CORPORATION ("LENDER").

                                    BACKGROUND
     A.   Lender has loaned Pepgen Corporation ("Borrower") $385,000 evidenced
by a secured promissory note of even date herewith (the "Note").  In order to
induce Lender to loan such $385,000 to Borrower, Guarantor, the Chairman of the
Board of Borrower, has agreed to personally guaranty the obligations of Borrower
under the Note.

                                   AGREEMENT
          GUARANTY.  Guarantor hereby guaranties the payment when due (whether
at stated maturity, by acceleration, or otherwise) of all obligations of
Borrower to Lender under the Note.  All obligations of Borrower to Lender under
the Note, including without limitation all obligations for principal and
interest, are referred to herein as the "Guarantied Obligations".  

     Guarantor shall pay to Lender all amounts payable by Guarantor hereunder
immediately upon demand.

          ABSOLUTE OBLIGATIONS.  The obligations of Guarantor hereunder are
absolute, independent, and unconditional under any and all circumstances (and a
separate action or actions may be brought to enforce this Guaranty), and no
invalidity or unenforceability of all or any part of the Guarantied Obligations,
or of all or any part of the Note shall affect, impair, or be a defense to this
Guaranty.  Without limiting the generality of the foregoing, no bankruptcy,
insolvency, liquidation, reorganization or similar proceeding involving or
affecting Borrower shall affect, impair, or be a defense to this Guaranty, and
no limitation on the liability of Borrower in such a proceeding shall diminish
or limit the liability of Guarantor hereunder.  In the event that Lender is
prevented, by operation of law or otherwise, from accelerating the Guarantied
Obligations or otherwise seeking to collect the Guarantied Obligations from, or
to enforce the Guarantied Obligations against, Borrower, in respect of any event
of default under the Note, Guarantor shall nevertheless pay the full amount of
the Guarantied Obligations as if the Guarantied Obligations had been
accelerated.

          CERTAIN AUTHORIZATIONS, WAIVERS AND CONSENTS.  

               In connection with its obligations under this Guaranty and the
Note, Borrower expressly:

                    authorizes Lender to, without notice to or demand on
Guarantor, and without releasing or exonerating Guarantor from any of his
Guarantied Obligations hereunder (including any release or exoneration that
might occur under any of Sections 2819, 2845, 2848, 2849 or 2850 of the
California Civil Code) or otherwise 


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affecting Guarantor's liability hereunder or under the Note, from time to 
time to, in Lender's absolute discretion:  (A) alter, compromise, renew, 
extend, accelerate, or otherwise change the time for payment of, or otherwise 
change the terms of the Guarantied Obligations or the Note, or any part 
thereof, including the increase or decrease of the rate of interest thereon 
and the increase in the amount of credit available thereunder or the advance 
otherwise of additional funds to or for the benefit of Borrower or any other 
Person (as defined in Section 3(b) below) obligated under the Guarantied 
Obligations; (B) take and hold security for the payment of the Guarantied 
Obligations or the obligations of Guarantor or any portion of any of the 
foregoing, and exchange, enforce, perfect, fail to perfect, waive, or release 
any such security; (C) release Borrower, or any other Person liable in 
respect of all or any portion of the Guarantied Obligations; (D) permit or 
suffer the impairment of any of the obligations of Borrower, or any other 
Person liable in respect of all or any portion of the Guarantied Obligations, 
in a case under the Bankruptcy Code by or against Borrower or any such 
Person; (E) permit or suffer the disallowance, avoidance or subordination of 
any of the Guarantied Obligations, or any obligations of any such Person and 
(F) apply payments received by Lender from Borrower, Guarantor or any such 
Person to any indebtedness of such payer to Lender, in such order as Lender 
shall determine in its sole discretion.

                    represents and warrants to Lender that Guarantor has
established adequate means of obtaining from Borrower, on a continuing basis,
financial and other information pertaining to Borrower's financial condition,
and agrees to keep adequately informed by such means of any facts, events or
circumstances which might in any way affect its risks hereunder, and Guarantor
further agrees that Lender shall not have any obligation to disclose to it any
information or material about Borrower or any other Person liable in respect of
all or any portion of the Guarantied Obligations that is acquired by Lender in
any manner;

                waives any and all rights and defenses based upon or arising by
reason of: (A) any disability or other defense of Borrower or any other Person;
(B) the cessation or limitation from any cause whatsoever, other than payment
and performance in full, of the obligations of Borrower or any other Person in
respect of the Guarantied Obligations or the obligations of Guarantor hereunder
and under the Note; (C) any lack of authority of any officer, director, partner,
agent, or any other Person acting or purporting to act on behalf of Borrower or
any other Person liable in respect of all or any portion of the Guarantied
Obligations, or any defect in the formation of Borrower or any such other
Person; (D) the application by Borrower or any other Person of the proceeds of
any of the Guarantied Obligations for purposes other than the purposes
represented by Borrower or any such other Person to Lender or Guarantor, or
intended or understood by Lender or Guarantor; (E) any act or omission by Lender
which directly or indirectly results in or aids the discharge of Borrower, or
any other Person, or any of the Guarantied Obligations, or the obligations of
Guarantor or any other Person by operation of law or otherwise; (F) any
modification of all or any portion of the Guarantied Obligations or of any other
Person under the Note, in any form whatsoever, and including, without
limitation, the renewal, extension, acceleration or other change in time for
payment of such obligations, or other change in the terms of such obligations or
any part thereof, including any increase or decrease of the rate of 


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interest thereon and any increase in the amount of credit available 
thereunder, (G) any act or occurrence authorized under subparagraph 3(a)(i) 
hereof or (H) any other statute or principle of law that would have the 
effect of exonerating Guarantor or limiting Guarantor's liability, or 
Lender's rights, hereunder.

          "Person" means an individual, partnership, corporation (including a
business trust), limited liability company, joint stock company, trust,
unincorporated association, joint venture or other entity, or a country or
political subdivision thereof or any agency or instrumentality of such country
or subdivision.     

          WAIVER OF NOTICE, ETC.  Guarantor waives to the fullest extent
permitted by applicable law:  (a) acceptance and notice of acceptance of this
Guaranty; (b) demands for the performance or observance of all or any of the
Guarantied Obligations; (c) presentment, protest, or notice of dishonor and
protest of the Guarantied Obligations; (d) notice of any extensions, consents,
or waivers given to Borrower or any other Person, notices of new or additional
indebtedness of Borrower or any other Person to Lender or any increase in the
Guarantied Obligations, and notice of the occurrence of any potential default or
event of default under the Note or of any other condition relating to the
financial condition of Borrower or of any other Person liable in respect of all
or any portion of the Guarantied Obligations; (e) any rights or claim of right
to cause a marshaling of Borrower's or any other Person's assets, or to cause
Lender to proceed against Borrower or any other Person in any particular order
and (f) any requirement of diligence or promptness on Lender's part in making
any claim or demand on or commencing against Borrower or otherwise enforcing
Lender's rights in respect of the Guarantied Obligations, this Guaranty or the
Note.

          BANKRUPTCY, REORGANIZATION, INSOLVENCY.  No obligation of Guarantor
under this Guaranty or the Note shall be altered, limited or affected by any
proceeding, voluntary or involuntary, involving the bankruptcy, insolvency,
receivership, reorganization, liquidation or arrangement of Borrower or any
other Person, or by any defense which Borrower or any other Person may have by
reason of the order, decree or decision of any court or administrative body
resulting from any such proceeding.  Guarantor acknowledges and agrees that any
interest on the Guarantied Obligations which accrues after the commencement of
any such proceeding (or, if interest on any portion of the Guarantied
Obligations ceases to accrue by operation of law by reason of the commencement
of said proceeding, such interest as would have accrued on any such portion of
the Guarantied Obligations if said proceedings had not been commenced) shall be
included in the Guarantied Obligations because it is the intention of the
parties that the Guarantied Obligations should be determined without regard to
any rule of law or order which may relieve Borrower or any other Person of any
portion of such Guarantied Obligations. This Guaranty shall continue to be
effective, or be reinstated, as the case may be, if at any time payment of any
of the Guarantied Obligations or any part thereof is rescinded or must otherwise
be restored or returned by Lender upon the insolvency, bankruptcy,
reorganization, moratorium, or other debtor relief proceeding of Borrower or any
other Person, or otherwise, all as though such payment had not been made.
Guarantor waives any right of the deferral or modification of Guarantor's
obligations hereunder by virtue of any such proceeding.


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          WAIVER OF RIGHTS, SUBROGATION, INDEMNITY, ETC.  Guarantor hereby
waives any right of subrogation, reimbursement, indemnification, or
contribution, or any similar right with respect to Borrower or any other Person
that relates in any way to any of the Guarantied Obligations, including any
rights arising under any of Sections 2787 through 2855 inclusive of the
California Civil Code.  If any amount is received by Guarantor in respect of any
such right in violation of the foregoing prohibition, Guarantor shall receive
such amount as the property of, or as trustee for, Lender, and shall pay such
amount over to Lender on account of the Guarantied Obligations in exactly the
form received, together with any required endorsement or assignment of
Guarantor, but without reducing or affecting in any manner the liability of
Guarantor under the other provisions of this Guaranty.
     
          OTHER RIGHTS OF LENDER.  All rights and remedies of Lender, whether
under this Guaranty or the Note, or by law, are separate and cumulative, and the
exercise of one shall not limit or prejudice the exercise of any other such
rights or remedies.  The waivers by Guarantor in this Guaranty shall not be
deemed exclusive of any additional waivers by Guarantor which may be deemed to
exist at law or in equity.  No delay or omission by Lender in exercising any
rights or remedies shall operate as a waiver thereof.  No waiver of any right or
remedy of Lender, and no modification or amendment of this Guaranty or consent
to any departure therefrom, shall be effective unless the same shall be in
writing and duly signed by Lender, as the case may be.  Any such written waiver
shall apply only to the particular instance specified therein and shall not
impair the further exercise of such right or remedy or of any other right or
remedy of Lender, and no single or partial exercise of any right or remedy under
this Guaranty shall preclude any other further exercise thereof or any other
right or remedy.

          SECURITY INTEREST.  Guarantor hereby expressly grants Lender a
security interest in his home, which security interest is evidenced by the deed
of trust attached as Exhibit A to the Note (the "Deed of Trust").  In the event
that Borrower has not paid the Note in full within two weeks of the date hereof,
including all interest due thereon, Lender may perfect such security interest by
filing the Deed of Trust in the office of recorder of deeds in the county in
which Guarantor's home is located.

          DURATION.  This Guaranty is a continuing guaranty and shall remain in
full force and effect until the Note has been terminated or has expired and all
of the Guarantied Obligations and any amounts payable by Guarantor under this
Guaranty or the Note has been indefeasibly paid in full; provided, however, that
this Guaranty shall be reinstated following such payment in full to the extent,
and under the circumstances, provided in Section 5 hereof, or if any additional
Guarantied Obligations are created by any subsequent note.

          MISCELLANEOUS.

               SUCCESSORS AND ASSIGNS.  This Guaranty shall be binding upon
Guarantor and his successors and assigns, and shall inure to the benefit of
Lender and its respective transferees, successors and assigns.  Lender may
assign (or otherwise 


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transfer) all or any part of its rights under this Guaranty in connection 
with any assignment or other transfer of all or any portion of its interest 
in the Guarantied Obligations.  Guarantor shall have no right to assign or 
transfer any of his rights or obligations hereunder.  

               SEVERABILITY.  If any provision of this Guaranty is held to be
invalid or unenforceable by a court of competent jurisdiction:  (i) this
Guaranty shall be construed as not containing such provision to the extent held
invalid or unenforceable, (ii) the other provisions of this Guaranty shall
remain in full force and effect, and (iii) the rights and obligations of the
parties hereto shall be construed and enforced accordingly to achieve the intent
of this Guaranty.

               GOVERNING LAW.  This Guaranty shall be construed in accordance
with and governed by the law of the State of California without reference to the
choice of law principles thereof.

               ATTORNEYS' FEES.  Guarantor agrees to pay reasonable attorneys'
and consultants' fees and expenses and all other costs and expenses incurred by
Lender  in the enforcement, interpretation or administration of this Guaranty
and the Note to which Guarantor is party, including, without limitation, all
reasonable out-of-pocket costs and expenses of Lender, if any, in connection
with any bankruptcy or other insolvency proceeding involving Borrower, Guarantor
or any other Person liable in respect of all or any portion of the Guarantied
Obligations.

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     IN WITNESS WHEREOF,  Guarantor has executed this Guaranty as of the day and
year first above written.

GUARANTOR AND HIS SPOUSE (IF HE IS MARRIED) ACKNOWLEDGE THAT CERTAIN LEGAL
RIGHTS GUARANTOR AND HIS SPOUSE MIGHT OTHERWISE HAVE HAD HAVE BEEN WAIVED UNDER
THIS GUARANTY.  GUARANTOR AND HIS SPOUSE EACH HAVE READ THIS GUARANTY AND
WARRANT THAT SUCH WAIVERS AND THEIR IMPLICATIONS ARE UNDERSTOOD.

GUARANTOR:

/s/ Chih-Ping Liu
---------------------------------------
Chih Ping Liu
                              
GUARANTOR'S SPOUSE (IF ANY):

/s/ Ko-Ming Liu
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(Signature)

Acknowledged and Agreed:

BORROWER:

/s/ Chih-Ping Liu
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Chih Ping Liu (C.P. Liu)
Title:  Chairman of the Board
      ---------------------------------