Here are some tips for using the plus sign.
1. Do not use the plus sign without a numeral.
Examples: +1, +2, +3, +4 or 1+, 2+, 3+, 4+
not +. ++, +++, ++++
2. In laboratory and technical readings, use the symbol unless it will not be noticeable or clear.
Example: 3+ gram-positive cocci
3. In a range, use the word to (not a hyphen) to indicate a range when the plus sign is used.
Example: Reflexes 2+/4 to 3+/4 on the right and 4+/4 on the left.
4. Write out plus when it means more than.
Example: At 40 plus, he considered himself old.
5. When typing “plus or minus,” express as plus or minus or plus/minus, not +/- except in tables or test results.
Diane Gilmore, CMT