FIRST AMENDMENT OF LEASE

         This First  Amendment  of Lease  ("Amendment")  is entered  into by and
between   The   City   of   Seattle,   a   Washington   municipal   corporation,
successor-in-interest-  to David A. Sabey and Sandra L. Sabey  ("Landlord"),  as
Landlord and Ostex International,  Inc., a Washington corporation ("Tenant"), as
Tenant,  under that certain Lease ("Lease"),  dated October 2, 1995, between the
parties hereto.

                                 R E C I T A L S

         A.  Landlord  and  Tenant  desire to  relocate  the third  (3rd)  floor
Building A Premises to the fourth  (4th) floor and to provide for certain  other
modifications  to the  Lease,  on the terms  and  conditions  contained  in this
Amendment.

         B.       Except as may be expressly provided otherwise in this
Amendment, capitalized terms in this Amendment shall have the

meaning given such terms in the Lease.

         NOW, THEREFORE, Landlord and Tenant agree as follows:

         1.       Amendments.

         1.1      Section 1.3 of the Lease regarding the Building A
Space is amended to add the following at the end of such

Section:

Notwithstanding the foregoing, commencing the earlier of: (i) January 1, 1997 or
(ii) the date on which Tenant occupies any of the fourth floor  relocation space
depicted on Exhibit B-2  attached  hereto  ("Fourth  Floor  Relocation  Space"),
Tenant's  Building A Space shall  automatically  be increased  by an  additional
12,307 net rentable square feet.  Commencing  January 1, 1997, Tenant may return
all or any portion of its  Premises on the third floor to Landlord  and Tenant's
obligation  to occupy and pay Rent for that portion of the third floor  Premises
so returned to Landlord shall then terminate. Landlord and Tenant shall document
any return of Tenant's  third floor  Premises to Landlord in a letter  agreement
which shall state the Base Rent payable by Tenant and Tenant's Share  adjustment
due to the return of such portion of the third floor Premises. Tenant shall have
completed its Tenant  improvements to the Fourth Floor Relocation Space and have
completely vacated its Premises on the third floor to Landlord's satisfaction no
later than  December 31,  1997,  at which time  Tenant's  Premises on Building A
shall consist of  approximately  24,832 net rentable square feet, which includes
the Phone Room,  described  below.  All square  footages  herein  described  are
subject to  recalculation  upon the finalization of Tenant's space plans for the
Fourth Floor


<PAGE>


Relocation  Space.   Tenant  acknowledges  that  it  accepts  the  Fourth  Floor
Relocation Space in its "AS-IS" condition. Notwithstanding the foregoing, Tenant
shall retain the  approximately  70 net rentable square feet of space located on
the third floor of the Building for its  telephone  and data room  identified on
Exhibit B-1  attached  hereto  ("Phone  Room") on the same terms and  conditions
contained in the Lease. Tenant shall have reasonable access to the Phone Room at
all times.  If Landlord later  determines  that the Phone Room must be relocated
due to restricted  access or another tenant's lease, the cost of such relocation
shall be borne equally by Tenant and Landlord.

         1.2      Section 1.4 of the Lease is amended to add the
following to the end of such Section:

         1.4 Tenant's  Share.  Notwithstanding  the foregoing,  effective on the
date that  Tenant  occupies  any of the Fourth  Floor  Relocation  Space  and/or
vacates any of its  Premises on the third floor in  accordance  with Section 1.3
above, "Tenant's Share of the Building" and "Tenant's Share of the Property" for
the  Building A Premises  shall be  increased  or  decreased  accordingly.  Upon
Tenant's  occupancy of the Fourth Floor Relocation  Space and Tenant's  complete
vacation  of its  Premises  on the  third  floor,  then  "Tenant's  Share of the
Building"  for the  Building A Premises  shall mean  twenty-five  and  fifty-two
one-hundredths  percent  (25.52%) and  "Tenant's  Share of the Property" for the
Building A Premises  shall mean  eight and  seventy-one  one-hundredths  percent
(8.71%).  All  square  footages  and  Tenant's  Share  amounts  are  subject  to
recalculation  upon the  finalization of Tenant's Fourth Floor  Relocation space
plans.

         1.3      Section 1.7 of the lease is amended and restated
in its entirety to read as follows:

         1.7      Expiration Date.  "Expiration Date" shall mean October
1, 2005, unless sooner terminated pursuant to the terms of this
Lease or extended pursuant to Section 3.1 of the Lease.

         1.4 The first  paragraph  of Section  2.3.1 of the Lease is amended and
restated as follows and the  remainder of Section 2.3.1 remains as stated in the
Lease:

         2.3.1.  Tenant's  Right of First  Refusal.  Provided  Landlord does not
require the third floor space  described  below in this  Section for its own use
now or in the Future,  and subject to the terms and  conditions  of this Section
2.3.1,  Landlord grants Tenant a right of first refusal during the Term to lease
all or any portion of the  remaining  space on the third floor of Building A and
that space in Building D depicted  as Suite 802 on Exhibit B-1 and Exhibit  B-3,
respectively ("First Refusal Space").


<PAGE>


         1.5 Section  2.3.2 of the Lease is amended to delete all  references to
the Building A Option Space from the Option for Tenant's  expansion  into Suites
300 and 310.

         1.6      Section 4.1.2 of the Lease is amended to add the
following at the end of such Section:

Notwithstanding the foregoing, commencing the earlier of: (i) January 1, 1997 or
(ii) the date on which Tenant first occupies any of the Fourth Floor  Relocation
Space,  the monthly  Base Rent for the Building A Space shall  automatically  be
increased to reflect the  inclusion of the Fourth Floor  Relocation  Space at an
annual per square  foot net charge of Twelve  and 50/100  Dollars  ($12.50)  and
reduced to reflect the return of the third floor Premises  pursuant to Amendment
1.1. Upon Tenant's vacation of all of the third floor Premises, Tenant's monthly
installment  of Base Rent shall be further  adjusted to reflect  such  vacation.
Commencing  October 1, 2000 through  October 1, 2005,  the Base Monthly Rent for
the Building A Space shall be increased to reflect an annual per square foot net
charge of Fourteen and No/100 Dollars ($14.00). All square footages and Tenant's
Base Rent amounts are subject to recalculation upon the finalization of Tenant's
Fourth Floor Relocation space plans.

         2.       Entire Amendment.  This Amendment sets forth the
entire agreement of the parties with respect to the subject
matter set forth herein and may not be modified other than by an
agreement in writing signed by the parties hereto or their
respective successors and interests.

         3.        Exhibits.  Exhibits B-1 and B-2 attached hereto are
incorporated herein by this reference and supersede and replace

the prior Exhibits B-1 and B-2.

         4. Acknowledgement.  The parties hereto each acknowledge that except as
expressly modified by this Amendment,  all the terms and conditions of the Lease
remain  unchanged and are in full force and effect and enforceable in accordance
with  their  terms.  In the  event of a  conflict  between  the  Lease  and this
Amendment, the terms and provisions of this Amendment shall control.

         DATED this _____ day of ___________, 1996.

LANDLORD:                           TENANT:

THE CITY OF SEATTLE                 OSTEX INTERNATIONAL, INC.

By:  ___________________   By: /S/ JOHN BRENNEMAN
Its: ___________________   Its: SECRETARY


<PAGE>


STATE OF WASHINGTON        )
                                    )  ss.

COUNTY OF KING             )

         On  this  ________  day  of   ______________,   1996,  before  me,  the
undersigned,  a  Notary  Public  in  and  for  the  State  of  Washington,  duly
commissioned      and      sworn      as     such,      personally      appeared
_____________________________,  to me known to be the  __________________ of THE
CITY OF  SEATTLE,  the  municipal  corporation  that  executed  the  within  and
foregoing  instrument,  and  acknowledged the said instrument to be the free and
voluntary  act and deed of said  corporation  for the uses and purposes  therein
mentioned,  and on oath  stated  that  he/she was  authorized  to  execute  said
instrument.

         WITNESS my hand and official seal the day and year in this  certificate
first above written.

                                    ------------------------------
                                    Printed Name: __________________
                                    NOTARY PUBLIC in and for the State
                                    of Washington, residing at

                                    ------------------------------
                                    My commission expires: _________

STATE OF WASHINGTON        )
                                    ) ss.

COUNTY OF KING             )

         On  this  15th  day  of   October,   1996,  before  me,  the
undersigned,  a  Notary  Public  in  and  for  the  State  of  Washington,  duly
commissioned      and      sworn      as     such,      personally      appeared
John M. Brenneman, to me known to be the Director of Finance of OSTEX
INTERNATIONAL,   INC.,  corporation  that  executed  the  within  and  foregoing
instrument,  and  acknowledged  the said instrument to be the free and voluntary
act and deed of said  corporation for the uses and purposes  therein  mentioned,
and on oath stated that he/she was  authorized to execute said  instrument,  and
that the seal affixed is the corporate seal of said corporation.

         WITNESS my hand and official seal the day and year in this  certificate
first above written.

                                    /s/ Mary J. Fabrizio
                                    Printed Name:  Mary J. Fabrizio
                                    NOTARY PUBLIC in and for the State
                                    of Washington, residing at

                                            Seattle, WA
                                    My commission expires:  1/15/99