There is no question that the most popular time of year to visit the Valley is in winter. This is partly because the rest of the country is experiencing it's worst weather of the year and in contrast, Phoenix seems like summer. So accept that any time after September and before May is probably best.
RSV: RSV in clinical medicine is the abbreviation for respiratory syncytial virus. See: Respiratory syncytial virus.
Updated April 20, 2016. Mean corpuscular volume (MCV) is a blood test that measures the average red blood cell volume, in other words, its size. MCV is part of a Complete Blood Count (CBC) test, and you will see it reported there along with other measures your red cells, white cells, and platelets.