Several years ago, my CD-57 levels were below range, don't remember just what they were. Years later, when mentioning this to my PCP, he said CD-57 could be low for other reasons. Didn't say what those reasons were. But,,I had read that low CD-57 levels could be indicative of Lyme disease. On, page 8 of Advanced Topics of Lyme (http://www.ilads.org/lyme_disease/B_guidelines_12_17_08.pdf) it states "It can even be used as a simple, inexpensive screening test, because at this point we believe that only Borrelia will depress the CD-57." Does anyone know of any reason, other than Lyme Borrelia, to explain low CD-57 levels?