The presence of certain signs, termed "red flags", indicate the need for further testing to look for more serious underlying problems, which may require immediate or specific treatment. The presence of a red flag does not mean that there is a significant problem. It is only suggestive, and most people with red flags have no serious underlying problem. If no red flags are present, performing diagnostic imaging or laboratory testing in the first four weeks after the start of the symptoms has not been shown to be useful.