Table of Contents

Locator Record

Title: Lower Extremity Disease – Ankle Brachial Blood Pressure Index (LEXAB_C )
Contact Number: 1-866-441-NCHS
Years of Content: 2003 - 2004
First Published: December, 2005
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Lower Extremity Disease
Record Source: NHANES 2003 - 2004
Survey Methodology: NHANES 2003 - 2004 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

The Lower Extremity Disease examination data will be used to determine the prevalence of lower extremity disease in the U.S. population (diagnosed and undiagnosed), including those at high risk for the late complications of the disease (i.e., ulceration and amputation). The major manifestations of lower extremity disease are peripheral vascular disease and peripheral neuropathy. The Ankle Brachial Blood Pressure Index section of the Lower Extremity Disease component collects data on peripheral vascular disease and the Peripheral Neuropathy section of the Lower Extremity Disease component collects data on peripheral neuropathy. The following documentation provides information on the ABPI section. Please refer to the LEXPN_C data file, codebook, and documentation for information on the Peripheral Neuropathy.

Eligible Sample

Participants 40 years of age and older are asked to participate in the ABPI Section of the Lower Extremity Disease examination.

Persons are excluded from the exam if they have a bilateral amputation or weigh over 400 pounds (due to equipment limitations). Additionally, some persons who were eligible for the exam (40 years of age and older) might not have received the exam due to the following multiple reasons:

  1. casts, ulcers, dressings, or other conditions of the participant interfered with testing;
  2. participant could not understand the test instructions;
  3. participant became ill and the test could not be performed;
  4. there was an equipment failure;
  5. participant refused;
  6. participant came late or left early from the MEC and the LED exam could not be performed; or
  7. some other reason. As a result, these eligible persons will have missing data for the ABPI variables.

The variable LEDSCCT2 may be used to identify reasons for missing data (refer to Analytic Notes section of this documentation for further details on the LEDSCCT2 variable). Because of participant confidentiality and data disclosure concerns, this file does not identify persons with a bilateral amputation. However, persons reporting right or left amputations of the feet and toes can be identified on the LEXPN_C data file, in variables LEALAMP and LEARAMP.

Protocol and Procedure

The ABPI exam was performed by trained health technicians in a specially equipped room in the mobile examination center (MEC). Participants lie supine on the exam table during the exam. Systolic pressure is measured on the right arm (brachial artery) and both ankles (posterior tibial arteries). If the participant has a rash or open wound on the right arm, dialysis shunt, right-sided radical mastectomy or any other condition that would interfere with accurate measurement or would cause discomfort to the participant, the left arm is used for the brachial pressure measurement. Systolic blood pressure is measured twice at each site for participants aged 40–59 years and once at each site for participants aged 60 years and older. If a health technician is unable to obtain a reading at a site, they may attempt another reading at the same site after a brief resting period. If the technician was unable to obtain even one ankle reading, they were asked to record whether they felt a posterior tibial pulse. If the technician recorded “yes”, they were asked if the participant’s posterior tibial systolic blood pressure was greater than 255 mm Hg.

Health technicians measured brachial and tibial systolic blood pressures using blood pressure cuffs with bladder widths of 9 cm, 12 cm, 15 cm, and 18 cm. The appropriate cuff to be used on a participant was determined by the circumference of the participant’s bare upper arm at the midpoint. While the participant was standing upright, the health technician would measure the participant’s arm circumference and then refer to the table below [adapted from Human Blood Pressure Determination by Sphygmomanometry by the American Heart Association (Perloff, 1993) ] to determine the acceptable cuff size for a given arm circumference. The same size cuff was used on the arm and both ankles with one exception. If the adult thigh cuff was used on the arm, the large adult cuff would be used on the participant's ankles. Also, if the technician was unable to make the adult thigh cuff fit properly on the participant's arm, the large adult cuff could be used instead. The information regarding the cuff exchange is recorded in variable LEQ020.

LEQ020 - Cuff Exchange
Cuff Size  Bladder Width (cm) Bladder Length (cm)  Arm Circumference (cm)
Child/small adult 9 17 17-21.9
Adult 12 22 22-29.9
Large adult 15 32 30-37.9
Adult thigh 18 35 38-47.9

After the appropriate cuff size was selected, the cuffs were placed on the participant’s arm and each ankle. Before the blood pressure was measured at each site, the peripheral neuropathy testing of the LED exam was performed to provide a brief resting period for stabilization of the participant’s blood pressure prior to measurement. (Note: the peripheral neuropathy protocol is described in a separate file (LEXPN_C).

For the procedures relevant to this component, please go to the Lower Extremity Disease Procedures Manual on the NHANES website.

Quality Assurance & Quality Control

Health technicians were regularly monitored by MEC supervisory staff and evaluated by experienced trainers and NCHS staff two to four times per year in the field. Retraining sessions were conducted with the technicians periodically and annually to reinforce the proper protocols and technique. Data were also routinely examined by outside staff.

Inspection, calibration, and maintenance of the equipment and supplies were performed on a regular basis. The NHANES Lower Extremity Disease Procedures Manual details the equipment quality control procedures.

For details on the QA/QC process for this component, please refer to the Procedure Manuals on the NHANES website.

Data Processing and Editing

During the data editing process, extreme values were examined. When there was insufficient information to conclude that values were invalid, they were retained in the data set. A few systolic blood pressure values below 40 mm Hg were considered implausible and set to missing. No other editing of the systolic blood pressure values was performed.

The ankle-brachial blood pressure index (ABPI) was automatically calculated by the computer system and verified by NCHS before data release. The right ABPI was obtained by dividing the mean systolic blood pressure in the right ankle by the mean blood pressure in the arm. The left ABPI was obtained by dividing the mean systolic blood pressure in the left ankle by the mean blood pressure in the arm. The mean blood pressure value for the arm and ankles are computed based on the first and second reading at each site. Because the second reading for all persons 60+ is missing, the mean values are in fact the first recorded blood pressure reading at a site. This may also be true for 40–59 year old persons who have a missing value for the first or second blood pressure reading.

Variable-Specific Editing:

LEDSCCT2 – ABPI Section Comment Variable

This variable is a quality control variable that NCHS used to monitor the LED component and the reasons technicians provided for why an exam was not done or was incomplete. Technicians were provided a defined list of reasons but could also select “other, specify” and provide the reason for a not-done or incomplete exam in a separate text field. Several of these “other” reasons were re-coded to one of the specific reasons (1–104), and the remaining were left as “other”.

Analytic Notes

Analysts should examine the data distribution and consider whether or not it is appropriate to include or exclude extreme values in a given analysis. Analysts should note that the absolute difference between the first and second systolic blood pressure reading (when available) was mostly between 0–10 mm Hg. There were cases where the difference was greater than 10 mm Hg.

Persons aged 40–59 may have up to two recorded blood pressure readings at each site, whereas persons aged 60 and older would only have one recorded reading at each site. Therefore, analysts should note that for participants aged 60 and older, all second measurements will be missing at each site. Other missing blood pressure values (either the first or second for those 40–59 or the first reading for those 60+) may have been due to one of many reasons, as described above, such as participant refusal, equipment failure, or technical error.

LEDSCCT2 – ABPI Section Comment Variable

This variable is a quality control variable that allowed NCHS to monitor the component and the reasons technicians provided for why an exam was not done or incomplete. The data were not collected for analytic reasons but for quality control purposes. This variable is only provided in the data release file to allow analysts to have some information on missing data and possible reasons for non-response.

Please refer to the Analytic Guidelines for further details on the use of sample weights and other analytic issues at http://www.cdc.gov/nchs/nhanes/survey_methods.htm.

No data from this component currently exist in the Research Data Center.

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 40 YEARS - 150 YEARS

LEDSCCT2 - ABPI Section Comment

Variable Name:
LEDSCCT2
SAS Label:
ABPI Section Comment
English Text:
ABPI section comment
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0 None 2082 2082
1 Safety exclusion 7 2089
2 SP refusal 139 2228
3 No time 45 2273
4 Physical limitation 100 2373
5 Communication problem 4 2377
6 Equipment failure 16 2393
7 SP ill/emergency 10 2403
14 Interrupted 2 2405
22 Pain or discomfort 7 2412
23 Poor cuff fit 8 2420
56 Came late/left early 69 2489
58 Unable to obtain all bps 565 3054
72 Error (technician/software/supply) 1 3055
84 SP with child 12 3067
101 Bandage, stocking, or other obstruction 4 3071
104 Swollen legs/ankle edema 2 3073
999 Other, specify 13 3086
. Missing 0 3086

LEAARM - Arm tested

Variable Name:
LEAARM
SAS Label:
Arm tested
English Text:
Arm tested
English Instructions:
DEFAULT IS RIGHT.
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Right 2744 2744
2 Left 34 2778
8 Could not obtain 5 2783
. Missing 303 3086

LEAARMC - Arm comment

Variable Name:
LEAARMC
SAS Label:
Arm comment
English Text:
Arm comment
English Instructions:
REASON FOR NOT USING RIGHT ARM.
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Lesion, bandage 18 18
2 Rash 0 18
3 Amputation 0 18
4 Other 21 39
. Missing 3047 3086

LEDARMCF - Brachial cuff size used

Variable Name:
LEDARMCF
SAS Label:
Brachial cuff size used
English Text:
Brachial cuff size used for BP measurement
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 9 cm 6 6
3 12 cm 757 763
4 15 cm 1878 2641
5 18 cm 104 2745
8 Could not obtain 8 2753
. Missing 333 3086

LEQ020 - Large adult used, poor thigh cuff fit

Variable Name:
LEQ020
SAS Label:
Large adult used, poor thigh cuff fit
English Text:
Large adult cuff selected due to poor thigh cuff fit?
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 244 244
2 No 1634 1878
. Missing 1208 3086

LEAANKL - Ankle(s) tested

Variable Name:
LEAANKL
SAS Label:
Ankle(s) tested
English Text:
Ankle(s) tested
English Instructions:
DEFAULT IS BOTH.
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Right 8 8
2 Left 6 14
3 Both 2760 2774
8 Could not obtain 4 2778
. Missing 308 3086

LEAANKLC - Ankle comment

Variable Name:
LEAANKLC
SAS Label:
Ankle comment
English Text:
Ankle comment
English Instructions:
REASON FOR NOT USING BOTH ANKLES.
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Edema, lesions, bandages 11 11
2 Rash 0 11
3 Amputation 6 17
4 Other 1 18
. Missing 3068 3086

LEDANKCF - Ankle cuff size used

Variable Name:
LEDANKCF
SAS Label:
Ankle cuff size used
English Text:
Ankle cuff size used for BP measurement
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 9 cm 6 6
3 12 cm 773 779
4 15 cm 1966 2745
5 18 cm 0 2745
8 Could not obtain 5 2750
. Missing 336 3086

LEXBRP1 - Brachial SBP 1 (mm Hg)

Variable Name:
LEXBRP1
SAS Label:
Brachial SBP 1 (mm Hg)
English Text:
Brachial systolic blood pressure 1 (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 150 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
57 to 250 Range of Values 2642 2642
. Missing 444 3086

LEXBRP2 - Brachial SBP 2 (mm Hg)

Variable Name:
LEXBRP2
SAS Label:
Brachial SBP 2 (mm Hg)
English Text:
Brachial systolic blood pressure 2 (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 59 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
55 to 217 Range of Values 1066 1066
. Missing 2020 3086

LEXBRPM - Mean Brachial SBP (mm Hg)

Variable Name:
LEXBRPM
SAS Label:
Mean Brachial SBP (mm Hg)
English Text:
Mean brachial systolic blood pressure (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 150 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
56 to 250 Range of Values 2658 2658
. Missing 428 3086

LEXLPTS1 - Left Posterior Tibial SBP 1 (mm Hg)

Variable Name:
LEXLPTS1
SAS Label:
Left Posterior Tibial SBP 1 (mm Hg)
English Text:
Left posterior tibial systolic blood pressure 1 (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 150 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
52 to 248 Range of Values 2348 2348
. Missing 738 3086

LEXLPTS2 - Left Posterior Tibial SBP 2 (mm Hg)

Variable Name:
LEXLPTS2
SAS Label:
Left Posterior Tibial SBP 2 (mm Hg)
English Text:
Left posterior tibial systolic blood pressure 2 (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 59 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
65 to 230 Range of Values 964 964
. Missing 2122 3086

LEXLPTSM - Left Mean Posterior Tibial SBP (mm Hg)

Variable Name:
LEXLPTSM
SAS Label:
Left Mean Posterior Tibial SBP (mm Hg)
English Text:
Left mean posterior tibial systolic blood pressure (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 150 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
52 to 248 Range of Values 2370 2370
. Missing 716 3086

LEXLABPI - Left ABPI

Variable Name:
LEXLABPI
SAS Label:
Left ABPI
English Text:
Left ABPI
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.33 to 2.16 Range of Values 2346 2346
. Missing 740 3086

LEXRPTS1 - Right Posterior Tibial SBP 1 (mm Hg)

Variable Name:
LEXRPTS1
SAS Label:
Right Posterior Tibial SBP 1 (mm Hg)
English Text:
Right posterior tibial systolic blood pressure 1 (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 150 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
61 to 248 Range of Values 2347 2347
. Missing 739 3086

LEXRPTS2 - Right Posterior Tibial SBP 2 (mm Hg)

Variable Name:
LEXRPTS2
SAS Label:
Right Posterior Tibial SBP 2 (mm Hg)
English Text:
Right posterior tibial systolic blood pressure 2 (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 59 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
76 to 232 Range of Values 973 973
. Missing 2113 3086

LEXRPTSM - Right Mean Posterior Tibial SBP (mm Hg)

Variable Name:
LEXRPTSM
SAS Label:
Right Mean Posterior Tibial SBP (mm Hg)
English Text:
Right mean posterior tibial systolic blood pressure (in millimeters of mercury)
Target:
Both males and females 40 YEARS - 150 YEARS
Hard Edits:
0.0000 to 300.0000
Code or Value Value Description Count Cumulative Skip to Item
61 to 248 Range of Values 2364 2364
. Missing 722 3086

LEXRABPI - Right ABPI

Variable Name:
LEXRABPI
SAS Label:
Right ABPI
English Text:
Right ABPI
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
0.36 to 2.07 Range of Values 2339 2339
. Missing 747 3086

LEALPTPD - Left PT pulse detected?

Variable Name:
LEALPTPD
SAS Label:
Left PT pulse detected?
English Text:
Left posterior tibial pulse detected?
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 275 275
2 No 54 329
8 Could not obtain 0 329
. Missing 2757 3086

LEARPTPD - Right PT pulse detected?

Variable Name:
LEARPTPD
SAS Label:
Right PT pulse detected?
English Text:
Right posterior tibial pulse detected?
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 277 277
2 No 53 330
8 Could not obtain 0 330
. Missing 2756 3086

LEALAPNC - Left ankle SBP > 255 mm Hg?

Variable Name:
LEALAPNC
SAS Label:
Left ankle SBP > 255 mm Hg?
English Text:
Left ankle systolic blood pressure > 255 mm Hg?
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 43 43
2 No 231 274
8 Could not obtain 0 274
. Missing 2812 3086

LEARAPNC - Right ankle SBP > 255 mm Hg?

Variable Name:
LEARAPNC
SAS Label:
Right ankle SBP > 255 mm Hg?
English Text:
Right ankle systolic blood pressure > 255 mm Hg?
Target:
Both males and females 40 YEARS - 150 YEARS
Code or Value Value Description Count Cumulative Skip to Item
1 Yes 45 45
2 No 231 276
8 Could not obtain 0 276
. Missing 2810 3086