The crteria for determinining an individual's HIV status using the Western Blot varies with respect to the location where the test is carried out. Could this have a bearing on false positives? Could it affect the statistics of HIV?AIDS occurence?

The western blot is almost always used as a confirmatory test after a positive enzyme linked immunoassay result. A western blot test should not be done in the absence of performing the enzyme linked immmunoassay. Your question, I believe, is making reference to the topic of HIV testing in low HIV prevalence areas/populations that can lead to "false positive" or "indeterminate" HIV test results. ("False negative" results have been most often reported during acute or recent HIV infection). In any event, repeat serologic HIV testing is almost always indicated in the first instance especially if the patient's viral load is below the level of detection. I should add that false positive HIV test results are extremely rare and, therefore, do not impact large scale reporting of HIV/AIDS statistics.