AMENDMENT TO SECURITIES PURCHASE AGREEMENT



      THIS AMENDMENT (this  "Amendment") to Securities  Purchase  Agreement (the
"Purchase  Agreement")  is  made as of  April  4,  2005,  by and  among  Calypte
Biomedical  Corporation,   a  Delaware  corporation  (the  "Company"),  and  the
Investors   identified  on  the  signature  pages  hereto   (collectively,   the
"Investors"). Unless otherwise defined herein, all capitalized terms used herein
shall have the  meanings  given to them in the  Purchase  Agreement  referred to
below.

      WHEREAS,  the Company and the Investors are parties to Securities Purchase
Agreements dated as of May 28, 2004 or July 9, 2004 (collectively, the "Purchase
Agreement");

      WHEREAS,  pursuant to the Purchase Agreement, in the event of the issuance
of Common Stock or Common Stock  Equivalents  at a purchase price per share less
than the Threshold  Price, the Investors are entitled to immediately (i) receive
Additional  Shares as set  forth in the  Purchase  Agreement,  (ii)  adjust  the
Exercise Price under the Warrant, and (iii) receive additional Warrant Shares as
set forth under the Warrant, (collectively, the "Anti-Dilution Entitlements");

      WHEREAS,  the Company  proposes  to issue and sell  certain  Common  Stock
Equivalents  and enter into definitive  agreements in connection  therewith (the
"Financing"), which would trigger the Anti-Dilution Entitlements;

      WHEREAS,  the  Investors  holding a majority of the Shares (the  "Required
Investors")  are  willing,  subject  to  the  terms  hereof,  to  amend  certain
provisions of the Purchase  Agreement and the Warrants so that the Anti-Dilution
Entitlements  that would be triggered as a result of the Financing do not become
effective  unless and until approved by the  stockholders of the Company,  which
approval the Company will first seek at its annual meeting of stockholders to be
held on or about June 7, 2005 (the "Meeting");

      WHEREAS, in consideration of the foregoing, the Company agrees to issue to
each Investor  Additional  Shares (as  hereinafter  defined),  other  additional
shares of Common Stock as described in Section 3 and  additional  Warrant Shares
(collectively,  the "New  Entitlements") on the terms and conditions and as more
particularly set forth herein; and

      WHEREAS,  the parties agree to amend and modify the Purchase  Agreement to
provide for certain other  modifications and amendments agreed to by the parties
in  accordance  with the  provisions  set forth in Section  6.4 of the  Purchase
Agreement.

      NOW,  THEREFORE,  for good and  valuable  consideration,  the  receipt and
sufficiency  of which are hereby  acknowledged,  the Company and each  Investor,
severally and not jointly, agree as follows:

1.1.  Section 4.7 of the Purchase  Agreement  is hereby  amended and restated to
read in its entirety as follows:

                  "Section 4.7. Additional Shares. If, prior to the first year
         anniversary of the Closing Date, the Company issues any shares of
         Common Stock or the Company or any Subsidiary issues any Common Stock
         Equivalents entitling any Person to acquire shares of Common Stock at a
         price per share less than less than the Threshold Price (if the holder
         of the Common Stock or Common Stock Equivalent so issued shall at any
         time, whether by operation of purchase price adjustments, reset
         provisions, floating conversion, exercise or exchange prices or
         otherwise, or due to warrants, options or rights issued in connection
         with such issuance, be entitled to receive shares of Common Stock at a
         price less than the Threshold Price, such issuance shall be deemed to
         have occurred for less than the Threshold Price), then, in connection
         with each such issuance of Common Stock or Common Stock Equivalents for
         a purchase price that is less than the Threshold Price, the Company
         shall issue additional shares of Common Stock (the "Additional Shares")
         to each Investor for no additional consideration. The number of
         Additional Shares issuable to each Investor will equal: (a) the
         Threshold Price minus the lowest price per share of the Common Stock or
         Common Stock Equivalents offered or sold that trigger an obligation
         under this Section divided by (b) the Threshold Price, multiplied by
         (c) the number of Shares issued to such Investor at the Closing
         pursuant to Section 2.2(a)(i). Additional Shares may not be issued
         under this paragraph unless and until this provision is approved by the
         stockholders of the Company in accordance with the rules and
         regulations of the American Stock Exchange, which approval the Company
         will first seek at the Meeting. Any issuances of Additional Shares that
         otherwise would have occurred prior to obtaining such stockholder
         approval, but which cannot hereunder be issued until such approval is
         obtained, will be carried forward until, and will become effective and
         be made at, such time as such approval is obtained.

                  The Additional Shares shall be entitled to the registration
         and other rights set forth in the Registration Rights Agreement
         (including the piggy-back registration rights thereunder). In addition,
         if the stockholders of the Company approve the issuance of Additional
         Shares at the Meeting, the Company will use its best efforts to
         register such Additional Shares no later than July 15, 2005.

                  Notwithstanding the foregoing, no issuances of Additional
         Shares will be made under this Section as a result of: (i) the issuance
         of Warrant Shares, (ii) the issuance of securities upon the exercise or
         conversion of any Common Stock or Common Stock Equivalents issued by
         the Company prior to the date hereof (but will apply to any amendments,
         modifications and reissuances thereof), (iii) the grant of options or
         warrants, or the issuance of additional securities, under any duly
         authorized Company stock option, restricted stock plan or stock
         purchase plan whether now existing or approved by the Company and its
         stockholders in the future (but not as to any amendments or other
         modifications to the number of Common Stock issuable thereunder, the
         terms set forth therein, or the exercise price set forth therein,
         unless such amendments or other modifications are approved by the
         Company's stockholders), (iv) up to an aggregate of 500,000 shares of
         Common Stock (including any shares of Common Stock issuable in respect
         of Common Stock Equivalents) issued or issuable as part of an equipment
         financing line in the ordinary course of business or a modification to
         the existing MTVB facility, approved by the Company's Board of
         Directors, in each case, at a price not less than the market price of
         the Common Stock at the time of the issuance, (v) issuance of shares of
         Common Stock to Logisticorp and Southwest Resource Preservation, Inc.,
         based upon the issuance and conversion of outstanding convertible
         debentures, with the issuance of said Common Stock not to exceed
         700,000 shares, or (vi) the grant of options and warrants to
         consultants for bona fide consulting services as approved by the
         Company's Board of Directors."

                                       2
<PAGE>

2.  Section  9(c) of the Warrant is hereby  amended and  restated to read in its
entirety as follows:

      "(c) Subsequent Equity Sales.

            (i) If the Company or any  subsidiary  thereof,  as applicable  with
respect  to  Common  Stock  Equivalents,  at any time  prior to the  first  year
anniversary  of the Closing Date,  shall issue any  securities of the Company or
any  Subsidiary  which entitle the holder thereof to acquire Common Stock at any
time, including without limitation,  any debt, preferred stock, rights, options,
warrants  or any  other  instrument  that  is at any  time  convertible  into or
exchangeable  for, or otherwise  entitles the holder thereof to receive,  Common
Stock or Common  Stock  Equivalents  entitling  any Person to acquire  shares of
Common Stock, at a price per share less than $0.40  (appropriately  adjusted for
any stock splits,  stock  combinations or similar events occurring prior to such
time) (if the holder of the Common  Stock or Common Stock  Equivalent  so issued
shall at any time,  whether by operation of purchase  price  adjustments,  reset
provisions,  floating conversion,  exercise or exchange prices or otherwise,  or
due to warrants,  options or rights issued in connection with such issuance,  be
entitled  to  receive  shares  of  Common  Stock  at a  price  less  than  $0.40
(appropriately  adjusted for any stock  splits,  stock  combinations  or similar
events  occurring  prior to such time)),  such issuance  shall be deemed to have
occurred for less than $0.40 (appropriately adjusted for any stock splits, stock
combinations  or similar  events  occurring  prior to such time)),  then, at the
option of the Holder for such exercises as it shall indicate, the Exercise Price
shall be multiplied by a fraction, the numerator of which shall be the number of
shares of Common  Stock  outstanding  immediately  prior to the issuance of such
shares of Common  Stock or such  Common  Stock  Equivalents  plus the  number of
shares of Common Stock which the offering  price for such shares of Common Stock
or Common  Stock  Equivalents  would  purchase at the  Exercise  Price,  and the
denominator  of which  shall be the sum of the number of shares of Common  Stock
outstanding  immediately  prior to such  issuance  plus the  number of shares of
Common Stock so issued or issuable. Adjustments to the Exercise Price under this
paragraph shall not become effective unless and until this provision is approved
by the  stockholders of the Company in accordance with the rules and regulations
of the American  Stock  Exchange,  which approval the Company will first seek at
the Meeting.  Any  adjustments  that would have occurred prior to obtaining such
stockholder approval,  but which cannot hereunder be made until such approval is
obtained, will be carried forward until, and will become effective at, such time
as such approval is obtained.  Notwithstanding the foregoing, no adjustment will
be made under this Section 9(c) in respect of:

                  (1) any grant of an  option or  warrant  for  Common  Stock or
issuance  of any shares of Common  Stock  upon the  exercise  of any  options or
warrants to employees,  officers and directors of or  consultants to the Company
pursuant to any stock option plan,  employee stock purchase plan or similar plan
or  incentive  or  consulting  arrangement  approved by the  Company's  board of
directors;

                  (2) any  restricted  stock  awards  approved by the  Company's
Board of Directors;


                                       3
<PAGE>

                  (3) shares of Common Stock or Common Stock Equivalents  issued
as consideration for the acquisition of another company or business in which the
shareholders of the Company do not have an ownership interest, which acquisition
has been approved by the Board of Directors of the Company;

                  (4)  any  rights  or  agreements  to  purchase   Common  Stock
Equivalents  outstanding on the date hereof and as specified in Schedule  3.1(g)
to the Purchase  Agreement (but not as to any amendments or other  modifications
to the number of Common Stock issuable thereunder,  the terms set forth therein,
or the exercise price set forth therein);

                  (5)  issuance  of shares of Common  Stock to  Logisticorp  and
Southwest Resource Preservation, Inc., based upon the issuance and conversion of
outstanding convertible  debentures,  with the issuance of said Common Stock not
to exceed 700,000 shares; or

                  (6) up to an  aggregate  of  500,000  shares of  Common  Stock
(including  any shares of Common  Stock  issuable  in  respect  of Common  Stock
Equivalents)  issued or issuable as part of an equipment  financing  line in the
ordinary  course of business or a  modification  to the existing MTVB  facility,
approved by the Company's Board of Directors,  in each case, at a price not less
than the market price of the Common Stock at the time of the issuance.

            (ii) If, at any time while this Warrant is outstanding,  the Company
or any  Subsidiary  issues  Common Stock  Equivalents  at a price per share that
floats or resets or otherwise varies or is subject to adjustment based on market
prices of the Common Stock (a "Floating Price  Security"),  then for purposes of
applying the preceding paragraph in connection with any subsequent exercise, the
Exercise  Price will be determined  separately on each Exercise Date and will be
deemed to equal the lowest price per share at which any holder of such  Floating
Price  Security is entitled to acquire  shares of Common Stock on such  Exercise
Date (regardless of whether any such holder actually acquires any shares on such
date)."

3. A new  provision  is hereby  added to the  Purchase  Agreement to read in its
entirety as follows:

                  "The parties agree that, subject to the approval of the
         stockholders in accordance with the rules and regulations of the
         American Stock Exchange, which approval the Company will first seek at
         the Meeting, in addition to (i) issuing Additional Shares pursuant to
         Section 4.7 of the Purchase Agreement, (ii) adjusting the Exercise
         Price pursuant to Section 9(c) of the Warrant, and (iii) issuing
         additional Warrant Shares pursuant to Section 9(d) of the Warrant, the
         Company will issue the following New Entitlements to each Investor: (x)
         additional shares of Common Stock equal to 5% of the Additional Shares
         issuable pursuant to Section 4.7 of the Purchase Agreement, (y)
         additional Warrant Shares issuable pursuant to Section 9(d) of the
         Warrant at a purchase price of $0.325, and (z) additional Warrant
         Shares equal to 5% of the additional Warrant Shares issuable pursuant
         to Section 9(d) of the Warrant for a purchase price of $0.325, all as
         more specifically set forth after each Investor's name on the table
         attached hereto as Exhibit A."

                                       4
<PAGE>

4. The parties agree that the New  Entitlements if approved by the  stockholders
of the Company at the Meeting, shall constitute Registrable Securities under the
terms of Registration Rights Agreement.

5. The Company shall use its reasonable best efforts to timely and properly call
the  Meeting,  and prepare and file a proxy  statement  with the  Commission  in
connection  therewith  requesting  stockholder  approval  of  the  Anti-dilution
Entitlements and the New Entitlements.

6. This Amendment shall not be binding upon the Company or the Investors  unless
and until each of the Required  Investors has delivered an executed copy of this
Amendment to the Company.

7. Except for the  amendments  provided for herein,  the  Transaction  Documents
shall remain unchanged and in full force and effect.

8. The  obligations  of each Investor  under this  Amendment are several and not
joint with the  obligations  of any other  Investor,  and no  Investor  shall be
responsible  in any way for the  performance  of the  obligations  of any  other
Investor  hereunder.  The decision of each Investor to enter into this Amendment
has been made by such  Investor  independently  of any other  Investor.  Nothing
contained  herein and no action taken by any Investor  hereunder shall be deemed
to constitute the Investors as a partnership, an association, a joint venture or
any other kind of entity,  or create a presumption that the Investors are in any
way  acting in  concert or as a group  with  respect  to this  Amendment  or the
transactions contemplated by the Transaction Documents.

9. This Amendment may be executed in any number of separate  counterparts,  each
of which shall be deemed to be an original,  but all of which  together shall be
deemed to be one and the same instrument.

10. This  Amendment  shall be governed by and construed in  accordance  with the
laws of the State of New York  without  giving  effect to the  conflicts  of law
principles thereof.

                            [Signature Pages Follow]


                                       5
<PAGE>

                        [SIGNATURE PAGE FOR THE COMPANY]

      IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart of
this Amendment  Agreement to be duly executed and delivered as of the date first
above written.


                                CALYPTE BIOMEDICAL CORPORATION


                                By:
                                   -------------------------------------
                                   Name:  Richard D. Brounstein
                                   Title: EVP and CFO


                                       6
<PAGE>

                         [SIGNATURE PAGE FOR INVESTORS]

      IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart of
this Amendment  Agreement to be duly executed and delivered as of the date first
above written.





                                               SF Capital Partners Ltd.
                                               ---------------------------------
                                               Name of Investor

                                               By:
                                                   -----------------------------
                                                  Signature

                                               Its:
                                                   -----------------------------
                                                   Title


                                               Marr Technologies BV
                                               ---------------------------------
                                               Name of Investor

                                               By:
                                                   -----------------------------
                                                  Signature

                                               Its:
                                                   -----------------------------
                                                   Title




                                               United Capital Partners LLC
                                               ---------------------------------
                                               Name of Investor

                                               By:
                                                   -----------------------------
                                                  Signature

                                               Its:
                                                   -----------------------------
                                                   Title

                                       7
<PAGE>

                                    EXHIBIT A
                         TABLE OF INVESTOR ENTITLEMENTS

                                                                 Additional
                                                                   shares
                                                                    (3)

Closing price - $8M Financing                                      $0.300
                                                                   ------

Common Stock Calculation
Additional shares/Million shares purchased (1)                    262,500

                                          Shares
                                        Purchased
May PIPE
SF Capital Partners LP                  10,000,000               2,625,000
Marr Technologies BV                     7,500,000               1,968,750
Proximity Fund                           1,250,000                 328,125
Proximity Partners                       1,250,000                 328,125
MTB Small Cap Growth
Fund                                     1,250,000                 328,125
MTB Multi Cap Growth
Fund                                     1,250,000                 328,125
Bridges & PIPES                            750,000                 196,875
                                                                 ---------
                                                                 6,103,125

July PIPE
United Capital Partners,
LLC                                      1,250,000                 328,125
Sunrise Equity Partners                  1,875,000                 492,188
Amnon Mandelbaum                           200,000                  52,500

David Goodfriend                            20,000                   5,250

TCMP3 Partners                             375,000                  98,438
                                                                  --------
                                                                   976,501
                                                                  --------
                                                                 7,079,626
                                                                 =========

(1) Based on the granting of an  additional  25,000  shares for each (cent) that
the Financing closes below $0.40, plus 5%


                                       8
<PAGE>

                              Exhibit A, Continued


------------------------------------ --------------- ---------------
Warrant Shares                       A Warrant $:             0.325
------------------------------------ --------------- ---------------
Warrant Shares                       B Warrant $:             0.325
------------------------------------ --------------- ---------------

All initial  warrants and additional  warrants will be  re-priced/priced  at the
closing  price of the Financing - based on the size of the  transaction  and the
outstanding  shares at closing - see note (5) Price and  number of new  warrants
will be fixed at closing.

--------------------------------------------------------------------
Warrant share calculation using assumed closing data:
--------------------------------------------------------------------

<TABLE>
<CAPTION>
                                                                        Dilution               New price
                                                                          factor
<S>                                  <C>             <C>                <C>              <C>
New shares                           At deal price   At $0.50 price
                                     -------------   --------------
 $8M @ $0.30 =                           26,666,667      16,000,000
 $60k fee @ $0.30 =                         200,000         120,000
                                     --------------- ---------------
                                         26,866,667      16,120,000
                                     --------------- ---------------
Series A exercised/100% =                26,866,667      17,463,334
Series B exercised/45% =                 12,090,000       7,858,500
Outstanding shares 3/31/05              171,207,589     171,207,589
                                     --------------- ---------------
Total dilution                          237,030,923     212,649,423       0.897138                0.45
                                     =============== ===============
</TABLE>

<TABLE>
<CAPTION>
                                                                                   Total warrants
                                                        Value @                         per             Additional     (inc. 5%)
                                     Warrant Shares       $0.50                    section 9 c) d)       Warrants      Additional
                                        Granted        per share                     per share            (2)(3)     Warrants (4)
                                        -------        ---------                     ---------            ------     ------------
<S>                                  <C>              <C>                          <C>                  <C>          <C>
May PIPE

SF Capital Partners LP                    3,500,000   $  1,750,000                       3,888,889          388,889        408,333
Marr Technologies BV                      2,625,000   $  1,312,500                       2,916,667          291,667        306,250
Proximity Fund                              437,500   $    218,750                         486,111           48,611         51,042
Proximity Partners                          437,500   $    218,750                         486,111           48,611         51,042
MTB Small Cap Growth Fund                   437,500   $    218,750                         486,111           48,611         51,042
MTB Multi Cap Growth Fund                   437,500   $    218,750                         486,111           48,611         51,042
Bridges & PIPES                             262,500   $    131,250                         291,667           29,167         30,625
                                                                                                       ------------- --------------
                                                                                                            904,167        949,376
July PIPE

United Capital Partners, LLC                875,000   $    437,500                         972,222           97,222        102,083
Sunrise Equity Partners                   1,312,500   $    656,250                       1,458,333          145,833        153,125
Amnon Mandelbaum                            140,000   $     70,000                         155,556           15,556         16,334
David Goodfriend                             14,000   $      7,000                          15,556            1,556          1,634
TCMP3 Partners                              262,500   $    131,250                         291,667           29,167         30,625
                                                                                                       ------------- --------------
                                                                                                            289,334        303,801
                                                                                                       ------------- --------------
                                     ---------------
                                         10,741,500                                                       1,193,501      1,253,177
                                     ===============                                                   ============= ==============
------------------------------------ --------------- --------------- -- --------------------------- -- ------------- --------------
New Warrant Price                           $  0.45                                                                       $  0.325
------------------------------------ --------------- --------------- -- --------------------------- -- ------------- --------------
</TABLE>

(2)   Warrants  will  result in  Additional  Shares if  exercise  occurs  before
      stockholder approval - assuming approval.

(3)   This amendment, once approved, will be offered to all investors in the May
      and  July  2004  PIPEs in  accordance  with  the  terms of the  respective
      agreements.

(4)   The  Additional  Warrants have been increased 5% under this Amendment with
      pricing at $0.325

(5)   This  Warrant  re-pricing  would be adjusted  if the closing  price of the
      Warrants is other than $0.325:

      Re-pricing  to $0.46 @ $0.365.  The Warrants are not  anti-dilutive  at or
      above $0.40.


                                       9