If I may again
. Fully cured paint:
a) is insoluble in water and most acids
b) other metals give the same black colour when in contact with H2S
c) Every single paint I tested over the last 10 years contains some lead. The question is not "does it contains the let?" (because it does). The question is how much. To be classified as "lead paint" material must contain 0.5% of lead or more. 0.49% is already not a "lead paint". Test kits or qualitative reactions cannot provide the accuracy you need. This why, as I mentioned earlier, that the test cannot be done without laboratory help (by the way, laboratory test in USA and Canada will cost you less than a test kit)
If your house was built before 1980, it likely contains lead paint. After 1982 lead paint was not used.