Table of Contents

Locator Record

Title: Hepatic/Gallbladder Ultrasound and Hepatic Steatosis (HGUHS )
Contact Number: 1-866-441-NCHS
Years of Content: 1988 - 1994
First Published: January, 2011
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Hepatic Gallbladder Ultrasound, Hepatic Steatosis, Fatty Liver
Record Source: NHANES 1988 - 1994
Survey Methodology: NHANES 1988 - 1994 is a stratified multistage probability sample of the civilian non-institutionalized population of the U.S.
Medium: NHANES Web site; SAS transport files

Component Description

Between 2009 - 2010, the hepatic steatosis (fatty liver) was assessed by re-reviewing the archived gall bladder ultrasound video images originally obtained in NHANES III between 1988 and 1994. The examination made it possible to grade the presence of fat within the hepatic parenchyma.

 

Eligible Sample

The ultrasound examinations were performed on adults aged 20 to 74 years who were examined in NHANES III. Fasting was preferred but not required.

 

Protocol and Procedure

Ultrasound examinations were originally recorded using a Toshiba Sonolayer SSA-90A and Toshiba video recorder. The examinations were performed using standardized procedures (Gallbladder Ultrasonography Procedure Manual, Third National Health and Examination Survey, http://www.cdc.gov/nchs/data/nhanes/nhanes3/cdrom/nchs/manuals/gallblad.pdf), which had been developed to ensure that each examination was performed in a consistent manner and that the results of each examination were accurate and reliable.

For the hepatic steatosis assessments, the video tapes of the NHANES III ultrasound examinations were digitized using a DVD-VHS Video cassette Recorder (SONY RDR-VX560) onto a Recordable DVD (Memorex, +R or +RW). DVD video-images were reviewed using a Dell Flat Panel Monitor (2408WFP, active matrix, thin-film transistor, liquid crystal display, 24-inch (609.6 mm) viewable area display, 1920 x 1200 resolution).

Three ultrasound readers were trained by a board certified radiologist who is specialized in hepatic imaging. Quality control and quality assurance procedures were used to standardize the reading form all readers (see below and Procedure Manual, Hepatic Steatosis). The following information was recorded on a standard paper collection form: 1) the presence of liver-to-kidney contrast 2) the degree of the brightness of the liver parenchyma, 3) the presence of deep beam attenuation, 4) the presence of echogenic walls in the small intrahepatic vessels, and 5) the definition of the gallbladder walls. Finally, an overall primary finding was given based on the presence or absence of each of the five parameters. The liver was graded as normal, mild, moderate, or severe hepatic steatosis.

For practical reasons, NHANES III Phase 2 ultrasounds were reviewed before Phase 1.

A more detailed description of the protocol is included in the Procedure Manual, Hepatic Steatosis, NCHS 2010. http://www.cdc.gov/nchs/data/nhanes/nhanes3/Hepatic_Steatosis_Ultrasound_Procedures_Manual.pdf

 

Quality Assurance & Quality Control

A radiologist, with 21 years of experience in the interpretation of ultrasound images, trained, observed, and validated the readers. Routine monitoring of the reliability (both inter- and intra-reader) was conducted every three months, throughout the study to detect if there was any need for re-training. For the training, the following steps were taken: 

1) All readers were required to read the relevant sections on hepatic ultrasound from "The Requisites Ultrasound" (Middleton et. al., 2004.); 

2) The readers met with the expert radiologist and reviewed a minimum of 100 ultrasound exams, from randomly selected NHANES III ultrasound video tapes. The key concepts were explained and demonstrated in detail using several exams;

3) The readers then re-reviewed the sample images from a library of more than 100 NHANES III examinations and external references images which were chosen as characteristic of a normal liver, a liver with mild-to-moderate hepatic steatosis, and a liver with severe hepatic steatosis;

4) The data collection form and procedures were also reviewed;

5) Additional exams (a minimum of 10 additional exams) were reviewed with the readers, until they demonstrated a good understanding of the concepts and procedures for reading the ultrasounds, and familiarity in completing the data form. The radiologist observed the readers to identify any reader difficulties and to ensure that findings are properly identified and documented;

6) A random sample of 100 NHANES III ultrasound exams were read by each reader separately and in random order and re-read at least one week apart. The kappa coefficient for inter- and intra-rater reliability was determined. Each reader was approved if their intra- and inter-rater kappa coefficients were ≥0.6. Should a reader fail to be approved, the training was repeated.

Throughout the study, each reader re-read a 5% randomly selected sample of the tapes s/he read previously and another 5% were re-read by another reviewer. Monitoring of the reliability results (both intra-rater and inter-rater) was conducted every three months. All ultrasound assessments for hepatic steatosis were conducted by readers who had no access to any other participant data.

A more detailed description of the Training, Quality Assurance and Quality Control is included in the Procedure Manual, Hepatic Steatosis, NCHS, 2010. http://www.cdc.gov/nchs/data/nhanes/nhanes3/Hepatic_Steatosis_Ultrasound_Procedures_Manual.pdf

 

Data Processing and Editing

The primary finding variable (GUPHSPF), is a 4 level variable. A primary finding recode (GUPHSPFR) variable was created from this variable. This is a two category variable: hepatic steatosis yes or no. The recode value of "Yes" indicates that moderate or severe hepatic steatosis was present. A recode value of "No" indicates that the liver was normal or had mild hepatic steatosis.

 

Analytic Notes

When analyzing these data, the MEC examination sample weight should be used (WTPFEX6). Users are encouraged to note carefully the "Instructions" describing, in brief, the various variables and suggested analysis in the codebook documentation. For more detailed information, readers should review the Procedure Manual (Hepatic Steatosis, NCHS 2010).Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues. Both of these are available on the NHANES website.

Users are encouraged to use the primary finding recode (GUPHSPFR) variable for all the analyses. This recode will help to avoid potential overlap between mild and moderate hepatic steatosis. The data file provides all the different parameters that were obtained for the assessment of hepatic steatosis: liver to kidney contrast, parenchymal brightness, deep beam attenuation, vessel walls definition, and gallbladder wall definition and the overall confidence in the assessment. These parameters should allow more experienced users to explore alternative criteria and to conduct sensitivity analyses.

GUPHSQC (Hepatic Steatosis assessment status comment) is a quality control variable that allowed NCHS to monitor the status of the assessment and the reasons readers provided why an exam was not analyzed or missing. The variable is provided in the data release file to allow analysts to have some information on missing data. Image is present, but ungradable may indicate any of the following: VHS tape was damaged, the ultrasound has a very poor quality that impairs the assessment of hepatic steatosis (e.g. presence of gas, patient examined in a wheelchair). No image reflects the fact that there was no ultrasound available for the participant.

In addition, for each of the above mentioned parameters (liver to kidney contrast, parenchymal brightness, deep beam attenuation, vessel walls definition, and gallbladder wall definition), in cases where the ultrasound technique and coverage did not include the parameter, then we marked "cannot assess" (coded as 9).

 

References

Codebook and Frequencies

SEQN - Respondent sequence number

Variable Name:
SEQN
SAS Label:
Respondent sequence number
English Text:
Respondent sequence number.
Target:
Both males and females 20 YEARS - 74 YEARS

GUPHSQC - HS Assessment Status

Variable Name:
GUPHSQC
SAS Label:
HS Assessment Status
English Text:
HS Assessment Status
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Image is present and gradable 13856 13856
7 Image is present, but ungradable 127 13983
8 No image 814 14797
. Missing 0 14797

GUPHSLKC - Liver to kidney contrast

Variable Name:
GUPHSLKC
SAS Label:
Liver to kidney contrast
English Text:
Liver to kidney contrast
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 No 6724 6724
2 Yes 3082 9806
7 Image is present, but ungradable 127 9933
8 No image 814 10747
9 Cannot assess 4050 14797
. Missing 0 14797

GUPHSPB - Parenchymal brightness

Variable Name:
GUPHSPB
SAS Label:
Parenchymal brightness
English Text:
Parenchymal brightness
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Normal 8372 8372
2 Mild 1059 9431
3 Moderate 2928 12359
4 Severe 1497 13856
7 Image is present, but ungradable 127 13983
8 No image 814 14797
9 Cannot assess 0 14797
. Missing 0 14797

GUPHSDBA - Deep beam attenuation

Variable Name:
GUPHSDBA
SAS Label:
Deep beam attenuation
English Text:
Deep beam attenuation
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Normal 10574 10574
2 Blurred 1888 12462
7 Image is present, but ungradable 127 12589
8 No image 814 13403
9 Cannot assess 1394 14797
. Missing 0 14797

GUPHSVW - Vessel walls

Variable Name:
GUPHSVW
SAS Label:
Vessel walls
English Text:
Vessel walls
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Normal 11482 11482
2 Absent 2366 13848
7 Image is present, but ungradable 127 13975
8 No image 814 14789
9 Cannot assess 8 14797
. Missing 0 14797

GUPHSDGB - Gallbladder wall

Variable Name:
GUPHSDGB
SAS Label:
Gallbladder wall
English Text:
Definition of gallbladder wall
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Normal 8826 8826
2 Blurred 3455 12281
3 Obliterated 599 12880
7 Image is present, but ungradable 127 13007
8 No image 814 13821
9 Cannot assess 976 14797
. Missing 0 14797

GUPHSPF - HS primary finding

Variable Name:
GUPHSPF
SAS Label:
HS primary finding
English Text:
HS primary finding
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Normal 8840 8840
2 Mild 1863 10703
3 Moderate 2134 12837
4 Severe 1019 13856
7 Image is present, but ungradable 127 13983
8 No image 814 14797
. Missing 0 14797

GUPHSPFR - HS primary finding, recode

Variable Name:
GUPHSPFR
SAS Label:
HS primary finding, recode
English Text:
HS primary finding, recode
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Normal-Mild 10703 10703
2 Moderate-Severe 3153 13856
7 Image is present, but ungradable 127 13983
8 No image 814 14797
. Missing 0 14797

GUPCHSC - Confidence in HS assessment

Variable Name:
GUPCHSC
SAS Label:
Confidence in HS assessment
English Text:
Confidence in HS assessment
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 None 43 43
2 Doubtful 898 941
3 Confident 7936 8877
4 Absolute 4979 13856
7 Image is present, but ungradable 127 13983
8 No image 814 14797
. Missing 0 14797

GUPHSREV - HS exam reviewer number

Variable Name:
GUPHSREV
SAS Label:
HS exam reviewer number
English Text:
HS exam reviewer number
Target:
Both males and females 20 YEARS - 74 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 1 8804 8804
2 2 3554 12358
3 3 1498 13856
7 Image is present, but ungradable 127 13983
8 No image 814 14797
. Missing 0 14797