Why would ana direct be positive 3 years, but then ifa method be negative? scl70 antibodies were elevated and still are at 5.2! direct false then?

ANA are being check : With two methods currently, one with ELISA, which is cheaper and more commercially available and read by machine. The other one with IFA, which is less prevalent, more expensive, more labor intense as it is interpreted by trained technician and of course the accuracy is better with latter. Scl70 antibody is important but without positive history and physical finding it is almost meaningless.