There are separate DNA tests for alpha and beta thal, so do find out if both were done. When you had the electrophoresis test, were levels given for HbA2 and HbF?
The test for lactate dehdrogenase isoenzymes is relevant here in that it may indicate hemolytic anemia. There is some degree of hemolytic anemia in most thal carriers, although it is assumed less for a silent alpha carrier. However, if you also carry beta, the level of hemolytic anemia would be higher, so that may have something to do with the diagnosis. Normally, carrying both somewhat cancels out the affects of the other, but you may experience a higher rate of hemolytic anemia when ill or taking certain meds, including some types of antibiotics and pain relievers. Basically, hemolytic anemia means you have a higher than normal turnover rate of red blood cells, and this is a feature of thalassemia.