How many patients with a normal Rhuematoid Factor has a positive measure of degree of coagulation?
normal Rhuematoid Factor refers TO RA IN('-', '+-'); positive measure of degree of coagulation refers to KCT = '+'; Should compute the number of distinct ones
SELECT COUNT(DISTINCT T1.ID) FROM Patient AS T1 INNER JOIN Laboratory AS T2 ON T1.ID = T2.ID INNER JOIN Examination AS T3 ON T3.ID = T2.ID WHERE (T2.RA = '-' OR T2.RA = '+-') AND T3.KCT = '+'