Exhibit 3.6


     REVISED CERTIFICATE OF CORRECTION FILED TO CORRECT A CERTAIN ERROR IN THE
     CERTIFICATE TO SET FORTH DESIGNATIONS, VOTING POWERS, PREFERENCES,
     LIMITATIONS, RESTRICTIONS, AND RELATIVE RIGHTS OF SERIES A 6% CUMULATIVE
     CONVERTIBLE PREFERRED STOCK, $0.001 PAR VALUE PER SHARE OF CHEMTRAK
     INCORPORATED FILED IN THE OFFICE OF THE SECRETARY OF STATE OF DELAWARE ON
     JANUARY 16, 1998

CHEMTRAK INCORPORATED hereby certifies that:

     1.   The name of the corporation is ChemTrak Incorporated, a Delaware
corporation.

     2.   That a CERTIFICATE OF CORRECTION FILED TO CORRECT A CERTAIN ERROR IN
THE CERTIFICATE TO SET FORTH DESIGNATIONS, VOTING POWERS, PREFERENCES,
LIMITATIONS, RESTRICTIONS, AND RELATIVE RIGHTS OF SERIES A 6% CUMULATIVE
CONVERTIBLE PREFERRED STOCK, $0.001 PAR VALUE PER SHARE was filed by the
Secretary of State of Delaware on January 20, 1998 and that said Certificate
requires correction as permitted under Section 103 of the General Corporation
Law of the State of Delaware.

     3.   The inaccuracy or defect of said Certificate to be corrected is
as follows: Article II, Section 5(f) included a clerical error.

     4.   Replace "Article II, Section 5(f)" with "Article II, Section 4(f)" and
make no other changes.

     IN WITNESS WHEREOF, said CHEMTRAK INCORPORATED has caused this Certificate
to be signed by Edward Covell, its President, and attested by Donald Fluken, its
Chief Financial Officer, this 19th day of February, 1998.

     Signed on this 19th day of February, 1998.

                              CHEMTRAK, INCORPORATED



                              By: /s/ Edward F. Covell
                                 ----------------------------------------------
                                     President


ATTEST:


/s/ Donald V. Fluken
- -------------------------------------------------
Chief Financial Officer