PPD result depend upon total induration area, again other test are also required to confirme the final diagnosis, the mantoux test
is not the sole criteria for tubercular infection
moreover the MT test in elderly patient is not much reliable, the Technic and administration with proper dose of ppd are also great matter, in your case , first thing you getting the partial relived with antibiotic but you again got the same complain it means that the infection does not autolysed completely , now biopsy
is only gold test you have, & this will clear over all picture, the further management are entirely depend upon histopath. test, take good care of your self.