NEW YORK – Here's an assignment to humble even the most confident doctor: Assess a patient's condition before millions of people without being able to examine him or see a complete medical chart.That, in effect, is what medical experts at news organizations have been asked to do since President Donald Trump revealed Friday that he had tested positive for COVID-19.They have a fine line to walk, needing to decide what level of speculation — if any — that they’re comfortable with, how much to read into medications the president has been prescribed and how to explain the course of a virus so new that it still confounds the people who study it.“You try to put the pieces of the puzzle together,” said CNN's Dr.