Mandatory Fifth Digit
A 3-digit code is the primary classification for an illness or injury, a 4-digit code is a secondary classification of the same illness or injury, and a 5-digit code is a classification of the same illness or injury.
Notes are also used to list the fifth-digit sub classifications for subcategories – such as entries “Tuberculosis” or Diabetes mellitus.” Only the four-digit code is given for the individual entry, and you must refer to the note following the main term to locate the appropriate fifth-digit sub classification.
Not all ICD codes are valid for use on insurance claim forms. Carriers require the greatest specificity possible when using the codes. The idea is never to use a 3-digit code that has been sub-classified into 4-digit codes, and never use a 4- digit code that has been sub-classified as a 5-digit code.
Not all codes have fourth and fifth digits, but when a fourth or fifth digit is available, it must be used. It is a good idea to highlight codes with which a fifth digit is listed. This will serve as a reminder to you to always use that fifth digit. The following is a list of fifth digits that are used to identify location.
0 site unspecified
1 shoulder region
2 upper arm
3 forearm
4 hand
5 pelvic region and thigh
6 lower leg
7 ankle and foot
8 other specified sites
9 multiple sites
