Q. Can one take a Covid test on Shabbat that involves the changing of color of the test paper?
A. On questio 23 regarding diapers with indicators that change color when wet, we wrote; Horav Shlomo Miller Shlit’”a is of the opinion that they could be used on Shabbos and Yom Tov since the melocho of Tzovea or dyeing is by definition a creative and positive act. However when it is done “’Derech Lichluch’” as staining or soiling it is not Tzovea. This is similar to the permitted use of a gauze in a wound smeared with blood or disposable paper napkins and tissues in cleaning colored spills.
The above is permitted even when it is done as a test or confirmation as in bedikah clothes or a wedding night bed sheet. See Mishna Berurah and Shaarei Tzion O.H. 320-20 , Biur Halocho O.C. 280, Sh’miras Shabbos 14-62.
Furthermore this is an indirect act, often done without intention (Gromo, Eino Miskaven) and therefore it is unlike diabetic urine test sticks, where Poskim are stringent when not totally necessary (Sh’miras Shabbos 33 (81).”
In our case The Rov maintains that the test when needed can be done with a Shinui or a variation from the normal procedure, such as holding the testing stick by one’s teeth,
Rabbi A. Bartfeld as advised by Horav Shlomo Miller, Horav Dovid Pam and Horav Aharon Miller Shlit’a.