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NASS Description of Data Elements
The Nationwide Ambulatory Surgery Sample (NASS) is a set of ambulatory surgery databases included in the HCUP family. These databases are created by AHRQ through a Federal-State-Industry partnership.
I10_NDX - Number of ICD-10-CM diagnoses on this discharge
Documentation Sections:
General Notes
Uniform Values
General Notes

I10_NDX indicates the total number of ICD-10-CM diagnoses (valid and invalid) coded on the discharge record. In assigning I10_NDX, the first listed diagnosis is included in the count, even if it is blank, so long as there is a secondary diagnosis present (see table below).

Beginning with the 2017 HCUP databases, external cause of morbidity codes are included with other diagnoses in the diagnosis-related data elements (I10_DXn, I10_NDX, and DXPOAn) and are no longer retained in separate data elements (I10_ECAUSEn, I10_NECAUSE, and E_POAn).

For data prior to the fourth quarter of 2015, the count of the number of diagnoses is stored in the data element NDX to indicate the use of the ICD-9-CM coding system.

Value Description
0 No ICD-10-CM diagnoses are coded on the record
1 Only the first listed diagnosis (I10_DX1) is coded. All secondary diagnoses are blank.
2 One secondary diagnosis (I10_DX2) is coded. The first listed diagnosis (I10_DX1) may be coded or blank.
3 The second and third diagnoses (I10_DX2 and I10_DX3) are coded. The first listed diagnosis (I10_DX1) may be coded or blank.
Uniform Values
VariableDescriptionValueValue Description
I10_NDXNumber of ICD-10-CM diagnoses on this discharge0-nnNumber of diagnoses

Internet Citation: HCUP NASS Description of Data Elements. Healthcare Cost and Utilization Project (HCUP). August 2019. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 8/14/19