Patients are being harmed by an increasing number of unregulated tests that guide medical treatment decisions. NECIR examined two testing arenas: Those for Lyme disease and a new generation of prenatal screening tests that identify the risk of Down syndrome and a growing list of other chromosomal abnormalities in a fetus. The stories, which took a total of six months to complete, gave readers a glimpse into the complex, confusing and highly competitive world of diagnostic tests. In some cases, patients are undergoing years of harmful, costly and unnecessary antibiotic treatment based on a questionable Lyme disease diagnosis. In others, women are terminating pregnancies because they - and their doctors - wrongly believe the results of a screening test for fetal problems are nearly 100 percent accurate.