Which volume serves as the alphabetic index for diseases?

The correct answer is the second volume, which serves as the alphabetic index for diseases. This volume is essential for healthcare professionals as it allows them to easily locate specific diseases by name, facilitating accurate coding and documentation. The alphabetical arrangement in this volume helps users quickly find the appropriate codes associated with various medical conditions, improving efficiency and reducing the likelihood of errors in recording diagnoses.

The other volumes, while important for different aspects of coding, do not function primarily as the alphabetic index. Volume 1 typically contains the tabular listing of diseases, where codes are organized in categories, while Volume 3 focuses on procedure coding. Volume 4 might provide additional guidance or resources but does not serve the specific purpose of an index for diseases.