Table of Contents

Locator Record

Title: Lower Extremity Disease (Ankle-Brachial Blood Pressure Index) (LEXAB_B )
Contact Number: 1-866-441-NCHS
Years of Content: 2001 - 2002
First Published: May, 2004
Revised: NA
Access Constraints: None
Use Constraints: None
Geographic Coverage: National
Subject:Ankle-Brachial Blood Pressure, lower extemity disease
Record Source: NHANES 2001 - 2002
Survey Methodology: NHANES 2001 - 2002 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_B 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 Component-Specific Analytic Notes section of this documentation for further details on the LEDSCCT2 variable). Due to participant confidentiality and data disclosure concerns, this file does not identify persons with a bilateral amputation. However, information on right or left amputations of the feet and toes is recorded on the LEXPN_B 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 9cm, 12cm, 15cm, and 18cm bladder widths. 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.

Table. Arm circumference and acceptable cuff size
Cuff Size   Bladder width (cm)  Bladder length (cm)  Arm circumference (cm)
 Child/small adult  9 17   17-21.9
 Adults  12  22  22-29.9
 Large adults  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_B).

Refer to Lower Extremity Disease Procedures Manual (National Center for Health Statistics, 2002) for further details.

 

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.

 

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. Since 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 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) for data release and the remaining were left as “other”.

LEDARMCF and LEDANKCF – Brachial cuff size used and Ankle cuff size used

These variables record the blood pressure cuff size used to obtain a systolic blood pressure measurement at the brachial and posterior tibial sites. To make these variables comparable with the 1999-2000 LED ABPI variables (LEDARMCF and LEDANKCF) and to aid in merging the 1999-2000 and 2001-2002 files, the values for the 2001-2002 variables were recoded to 1 (9 cm), 3 (12 cm), 4 (15 cm), 5 (18 cm), and 8 (could not obtain).

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 mm Hg and 10 mm Hg. There were cases where the difference was greater than 10 mm Hg.

Persons aged 40-59 may have up to 2 recorded blood pressure readings at each site where as persons aged 60 and older may only have 1 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 provided in the data release file to allow analysts to have some information on missing data and possible reasons for non-response.

 

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 2334 2334
1 Safety exclusion 1 2335
2 SP refusal 76 2411
3 No time 17 2428
4 Physical limitation 95 2523
5 Communication problem 2 2525
6 Equipment failure 4 2529
7 SP ill/emergency 16 2545
14 Interrupted 1 2546
22 Pain or discomfort 7 2553
43 Weight limitation on equipment 3 2556
56 Came late/left early 143 2699
58 Unable to obtain all bps 461 3160
72 Error (technician/software/supply) 2 3162
84 SP with child 15 3177
101 Bandage, stocking, or other obstruction 1 3178
103 As per doctor's request 1 3179
104 Swollen legs/ankle edema 1 3180
999 Other, specify 4 3184
. Missing 0 3184

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 2886 2886
2 Left 17 2903
8 Could not obtain 3 2906
. Missing 278 3184

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 0 0
2 Rash 1 1
3 Amputation 0 1
4 Other 18 19
. Missing 3165 3184

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 10 10
3 12 cm 770 780
4 15 cm 1918 2698
5 18 cm 163 2861
8 Could not obtain 7 2868
. Missing 316 3184

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 187 187
2 No 1731 1918
. Missing 1266 3184

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 11 11
2 Left 12 23
3 Both 2878 2901
8 Could not obtain 2 2903
. Missing 281 3184

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 12 12
2 Rash 1 13
3 Amputation 6 19
4 Other 6 25
. Missing 3159 3184

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 8 8
3 12 cm 774 782
4 15 cm 2083 2865
5 18 cm 0 2865
8 Could not obtain 1 2866
. Missing 318 3184

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
82 to 250 Range of Values 2813 2813
. Missing 371 3184

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
84 to 219 Range of Values 1367 1367
. Missing 1817 3184

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
82 to 250 Range of Values 2831 2831
. Missing 353 3184

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
53 to 239 Range of Values 2531 2531
. Missing 653 3184

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
52 to 236 Range of Values 1281 1281
. Missing 1903 3184

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
52.5 to 239 Range of Values 2612 2612
. Missing 572 3184

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
0.29 to 1.66 Range of Values 2604 2604
. Missing 580 3184

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
42 to 251 Range of Values 2546 2546
. Missing 638 3184

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
51 to 234 Range of Values 1272 1272
. Missing 1912 3184

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
42 to 251 Range of Values 2603 2603
. Missing 581 3184

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
0.23 to 1.62 Range of Values 2596 2596
. Missing 588 3184

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 167 167
2 No 54 221
8 Could not obtain 0 221
. Missing 2963 3184

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 178 178
2 No 48 226
8 Could not obtain 0 226
. Missing 2958 3184

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 30 30
2 No 136 166
8 Could not obtain 0 166
. Missing 3018 3184

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 38 38
2 No 140 178
8 Could not obtain 0 178
. Missing 3006 3184