This investigation led to a standardized scoring system used to assess a newborn's health after birth, with the result referred to as the newborn's "Apgar score". Each newborn is given a score of 0, 1 or 2 (a score of 2 meaning the newborn is in optimal condition, 0 being in distress) in each of the following categories: heart rate, respiration, color, muscle tone and reflex irritability. Compiled scores for each newborn can range between 0 and 10, with 10 being the best possible condition for a newborn. The scores were to be given to a newborn one minute after birth, and additional scores could be given in five-minute increments to guide treatment if the newborn's condition did not sufficiently improve. By the 1960s, many hospitals in the United States were using the Apgar score consistently. In the 21st century, the score continues to be used to provide an accepted and convenient method for reporting the status of the newborn infant immediately after birth .