National Hospital Discharge National Hospital Discharge Survey: A Hands-On WorkshopSurvey: A Hands-On Workshop

Using Public-Use Data FilesUsing Public-Use Data Files

Michelle N. Podgornik, MPHMichelle N. Podgornik, MPH

2006 Data Users Conference2006 Data Users ConferenceJuly 11, 2006July 11, 2006

8:30am-10:00am8:30am-10:00amSession #23Session #23

National probability survey of discharges from National probability survey of discharges from

non-federal, short-stay hospitals in the United non-federal, short-stay hospitals in the United

StatesStates

Conducted annually since 1965Conducted annually since 1965

Latest data available: 2004Latest data available: 2004

NHDS BackgroundNHDS Background

Three-Stage DesignThree-Stage Design

• Primary Sampling Units (PSUs)Primary Sampling Units (PSUs)

• HospitalsHospitals

• DischargesDischarges

NHDS DesignNHDS Design

AgeAge

SexSex

RaceRace

Source of paymentSource of payment

Discharge statusDischarge status

Marital statusMarital status

Patient DataPatient Data

Geographic regionGeographic region

Bed sizeBed size

OwnershipOwnership

Facility DataFacility Data

DiagnosesDiagnoses

Surgical and non-surgical proceduresSurgical and non-surgical procedures

International Classification of Diseases, 9International Classification of Diseases, 9 thth

Revision, Clinical Modification (ICD-9-CM)Revision, Clinical Modification (ICD-9-CM)

Medical DataMedical Data

Days of careDays of care

Month of dischargeMonth of discharge

Diagnosis-related groups (DRGs)Diagnosis-related groups (DRGs)

Analysis weightAnalysis weight

Additional DataAdditional Data

At the end of this session, you will be able to:At the end of this session, you will be able to:

• Understand some of the advantages and Understand some of the advantages and

limitations of using downloadable NHDS datalimitations of using downloadable NHDS data

• Successfully download data files from the Successfully download data files from the

Internet and create a SAS dataset for analysisInternet and create a SAS dataset for analysis

• Perform simple analyses using SASPerform simple analyses using SAS

Session GoalsSession Goals

AdvantagesAdvantages

• Obtain current data and data file documentationObtain current data and data file documentation

• Obtain diagnosis-related group (DRG) Obtain diagnosis-related group (DRG)

informationinformation

Using Online Data FilesUsing Online Data Files

LimitationsLimitations

• Only single-year data files from 1996 through Only single-year data files from 1996 through

2004 are available2004 are available

• Variables necessary to run SUDAAN are not Variables necessary to run SUDAAN are not

publicly availablepublicly available

Using Online Data FilesUsing Online Data Files

Download data and data file layout from the Download data and data file layout from the

NCHS website - NCHS website - http://www.cdc.gov/nchshttp://www.cdc.gov/nchs

Fixed width ASCII files are available for each Fixed width ASCII files are available for each

data collection year since 1996data collection year since 1996

Downloading DataDownloading Data

Downloaded data files must be “unzipped” Downloaded data files must be “unzipped”

using extraction software (e.g. WinZip)using extraction software (e.g. WinZip)

Your computer may have extraction software Your computer may have extraction software

pre-installed; if not, a free evaluation version pre-installed; if not, a free evaluation version

of WinZip is available at: of WinZip is available at:

http://www.winzip.com/downwzeval.htm?wzdmhttp://www.winzip.com/downwzeval.htm?wzdm

Extracting DataExtracting Data

Each document includes:Each document includes:

• A description of the NHDS, including survey A description of the NHDS, including survey

methodologymethodology

• File layoutFile layout

• Parameters and equations used to calculate Parameters and equations used to calculate

relative standard errors, a measure of the relative standard errors, a measure of the

reliability of an estimatereliability of an estimate

Data File DocumentationData File Documentation

Each document also includes:Each document also includes:

• ICD-9-CM code changesICD-9-CM code changes

• Census population estimatesCensus population estimates

• Unweighted and weighted frequencies of Unweighted and weighted frequencies of

selected variablesselected variables

• Medical Abstract FormMedical Abstract Form

Data File Documentation ( - cont’d - )Data File Documentation ( - cont’d - )

Select “Extract All…” from the drop-down menu

Double-click: Double-click: My ComputerMy Computer

Double-click:Double-click: Local Disk (C:)Local Disk (C:)

Double-click:Double-click: 2006 Data Users Conference2006 Data Users Conference

Double-click:Double-click: ExercisesExercises

Hands-On ExercisesHands-On Exercises

Creating a SAS datasetCreating a SAS dataset

Generating simple unweighted and weighted Generating simple unweighted and weighted

frequenciesfrequencies

Calculating first-listed, any-listed, and all-listed Calculating first-listed, any-listed, and all-listed

diagnosesdiagnoses

Calculating all-listed proceduresCalculating all-listed procedures

Hands-On ExercisesHands-On Exercises

Exercise #1Exercise #1

Creating a SAS datasetCreating a SAS dataset

Exercise #2Exercise #2

Generating simple unweighted frequenciesGenerating simple unweighted frequencies

Exercise #3Exercise #3

Generating simple weighted frequenciesGenerating simple weighted frequencies

Exercise #4Exercise #4

Calculating first-listed diagnosesCalculating first-listed diagnoses

DefinitionDefinition

First-listed diagnosisFirst-listed diagnosis

• Principal diagnosis (if specified) or the Principal diagnosis (if specified) or the

diagnosis listed first on the medical record face diagnosis listed first on the medical record face

sheetsheet

Exercise #5Exercise #5

Calculating any-listed diagnosesCalculating any-listed diagnoses

DefinitionDefinition

Any-listed diagnosisAny-listed diagnosis

• The occurrence of a diagnosis at least once in The occurrence of a diagnosis at least once in

a record, regardless of positiona record, regardless of position

Exercise #6Exercise #6

Calculating all-listed diagnosesCalculating all-listed diagnoses

DefinitionDefinition

All-listed diagnosisAll-listed diagnosis

• Total number of times (up to seven) that a Total number of times (up to seven) that a

diagnosis appears in a recorddiagnosis appears in a record

Exercise #7Exercise #7

Calculating all-listed proceduresCalculating all-listed procedures

DefinitionDefinition

All-listed procedureAll-listed procedure

• Total number of times (up to four) that a Total number of times (up to four) that a

procedure appears in a recordprocedure appears in a record

Reliability of EstimatesReliability of Estimates

Estimates should be based on at least 30 Estimates should be based on at least 30

sample recordssample records

Estimates should also have a relative Estimates should also have a relative

standard error (RSE) of less than 30 percentstandard error (RSE) of less than 30 percent

Combine multiple years of data until you have Combine multiple years of data until you have

at least 30 raw cases in cells of interestat least 30 raw cases in cells of interest

RSE improves with the number of years RSE improves with the number of years

combinedcombined

How To Increase ReliabilityHow To Increase Reliability

Multi-year data file CD-ROMMulti-year data file CD-ROM

• Admission month is available on the multi-year Admission month is available on the multi-year

data file but not on the single-year data filesdata file but not on the single-year data files

• Diagnostic-related group (DRG) information is Diagnostic-related group (DRG) information is

available on the single-year data files but not available on the single-year data files but not

on the multi-year data fileon the multi-year data file

• Order of variables slightly differentOrder of variables slightly different

Other Sources of Public-Use Other Sources of Public-Use DataData

Visit the NHDS website Visit the NHDS website

http://www.cdc.gov/nchs/nhds.htmhttp://www.cdc.gov/nchs/nhds.htm

Contact the Hospital Care Statistics Branch by Contact the Hospital Care Statistics Branch by

calling 301-458-4321 or by e-mailing calling 301-458-4321 or by e-mailing

nchsquery@cdc.govnchsquery@cdc.gov

How to Obtain More InformationHow to Obtain More Information

To request electronic copies of this To request electronic copies of this

PowerPoint presentation and the SAS PowerPoint presentation and the SAS

exercises, please send an e-mail to exercises, please send an e-mail to

Michelle Podgornik at Michelle Podgornik at cvn7@cdc.gov