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5. Anthropometric measurements

5.1 Equipment

For anthropometric measurements (weight, height, waist and hip circumference) the following equipment is needed:

• balanced beam scale;
• portable/wall mounted stadiometer with movable head piece, or measuring rod, typically mounted on balanced beam scales;
• flexible, but non-stretchable measuring tape or insertion tape;
• full body-length mirror with 10cm ´ 10 cm grid lines;
• carpenter's level;
• several calibrated weights (e.g. 10 kg or 20 kg each) that can be combined to give test weights between 50 kg and 100 kg;
• calibrated length rods of 150 cm and 200 cm.

5.2 Measurement procedures

5.2.1 Weight measurement

Weight should be measured in all participants, except pregnant women, wheelchair bound individuals, or persons who have difficulty standing steady.

Setting up scale at the examination site

The scale should be placed on a hard-floor surface (not on a floor which is carpeted or otherwise covered with soft material). If there is no such floor available, a hard wooden platform should be placed under the scale. A carpenter's level should be used to verify that the surface on which the scale is placed is horizontal.

Calibration of scale 

Calibration should occur at the beginning and end of each examining day.

The scale is balanced with both sliding weights at zero and the balance bar aligned. The scale is checked using the standardized weights and calibration is corrected if the error is greater than 0.2 kg. The results of the checking and the recalibrations are recorded in a log book.

Normal weighing procedure

1. Participants are asked to remove their heavy outer garments (jacket, coat, throusers, skirts, etc.) and shoes. If subjects refuse to remove trousers or skirt, at least make them empty their pockets and record the fact in the data collection form (see Appendix 5.1).
2. The participant stands in the centre of the platform, weight distributed evenly to both feet. Standing off-centre may affect measurement. (See Picture 5.1)
   
   
   Picture 5.1. Posture of the subject during the weight measurement
   
3. The weights are moved until the beam balances (the arrows are aligned). (See Picture 5.2) 
   
   
   Picture 5.2. Moving the weights to balance the beam
   
4. The weight is recorded to the resolution of the scale (the nearest 0.1 kg or 0.2 kg).

Weighing procedure for heavily overweight persons

If the participant is heavily overweight, i.e. weighs more than the upper limit of the scale, this fact should be noted in the data collection form, together with the upper limit of the scale (see Appendix 5.1).

Self-reported weight

Self-reported weights are not acceptable, even if the participant is immobile or refuses to be weighed.

5.2.2 Height measurement

Height should be measured in all participants, except wheelchair bound individuals, persons who have difficulty standing steady or straight, and participants with hairstyle (e.g. Afro or Mowhawk) or head dress (e.g. turban) that prevents proper use of the height measuring equipment.

Setting up stadiometer at the examination site

If the height is measured with the measuring rod attached to the balanced beam scale no further set-up procedures are required, if the scale has been placed properly for weighing. However, it should be verified that the upper part of the measuring rod is straight and vertical (i.e. not bend or curved).

If the height is measured by stadiometer, the height rule is taped vertically to the hard flat wall surface with the base at floor level. The wall may not have a baseboard molding. A carpenter's level is used to check the vertical placement of the rule.

The floor surface next to the height rule must be hard. If no such floor is available, a hard wooden platform should be placed under the base of the height rule. Using the carpenter's level, the surface on which the height rule rests should be checked to be horizontal.

Calibration of height rule 

At the beginning and end of each examination day, the height rule should be checked with standardized rods and corrected if the error is greater than 2 mm. The results of the checking and recalibrations are recorded in the log book.

Normal height measurement procedure

1. Participants are asked to remove their shoes, heavy outer garments, and hair ornaments. 
2. The participant is asked to stand with his/her back to the height rule. The back of the head, back, buttocks, calves and heels should be touching the upright, feet together. The top of the external auditory meatus (ear canal) should be level with the inferior margin of the bony orbit (cheek bone). The participant is asked to look straight. (See Picture 5.3)
   

   Picture 5.3 Position of the subject during the height measurement

3. The head piece of the stadiometer or the sliding part of the measuring rod is lowered so that the hair (if present) is pressed flat. (See Picture 5.4)
   
   Picture 5.4 Lowering of head piece of measuring tape
4. Height is recorded to the resolution of the height rule (i.e. nearest millimetre/half a centimetre). If the participant is taller than the measurer, the measurer should stand on a platform so that he/she can properly read the height rule. (See Picture 5.5) 
   
   Picture 5.5 Use of platform when measuring tall person

5. If a participant is excluded from height measurement, the reason should be recorded in the data collection form (see Appendix 5.1).

Height measurement procedure for very tall persons

If the participant is taller than the scale of the height rule, no height measurement should be made and this fact, together with the upper limit of the height rule, should be recorded in the data collection form (see Appendix 5.1). 

Self-reported height

Self-reported height is not acceptable, even if the participant is immobile or refuses to have his/her height measured.

5.2.3 Waist circumference measurement

Setting up the place for the waist circumference measurement

The full body length mirror is placed against the wall or if the mirror stands on its own feet next to the measurement place. Using the carpenter level, it should be verified that grid lines on the mirror are horizontal. 

Checking of tape 

The length of the measuring tape is checked with the calibrated length rod (usually the 150 cm one) at least once per month. If the measuring tape is stretched it should be replaced.

Position of waist circumference measurement

Waist circumference should be measured at a level midway between the lower rib margin and iliac crest with the tape all around the body in horizontal position. (See Picture 5.6)

Picture 5.6. Position of waist circumference measurement

Waist circumference measurement procedure

1. Participants are asked to remove their clothes, except for light underwear. If this is not possible, for example due to cultural reasons, the alternative is to measure the circumference on the subject without heavy outer garments and record this fact in the data collection form. Tight clothing, including the belt, should be loosened and the pockets emptied.
2. The measurer should stand at the side of the participant in order to have a clear view of the mirror. 
3. Participants should be standing with their feet fairly close together (about 12-15 cm) with their weight equally distributed to each leg. Participants are asked to breathe normally; the reading of the measurement should be taken at the end of gentle exhaling. This will prevent subjects from contracting their abdominal muscles or from holding their breath.
4. The measuring tape is held firmly, ensuring its horizontal position. Use the grid lines on the mirror to verify that the tape position is horizontal all around the waist.  The tape should be loose enough to allow the observer to place one finger between the tape and the subject's body. (See Picture 5.7) 
   
   
   Picture 5.7. The position of measuring tape and placement of one finger between the tape and the subject's body
   
5. Measurements are recorded to the resolution of the tape (nearest millimeter/half centimeter). 

Self-reported waist circumference

If the participant is immobile or refuses to have his/her waist circumference measured, this fact should be recorded in the data collection form. Self-reported waist circumference is not acceptable as a substitute.

Waist circumference exceeds the length of the tape

If the waist circumference exceeds the length of the tape, this fact should be recorded in the data collection form together with the maximum length of the tape (see Appendix 5.1).

5.2.4 Hip circumference measurement

Position of hip circumference measurement

Hip circumference should be measured as the maximal circumference over the buttocks. The grid lines on the mirror are used to verify that the tape position is horizontal all around the body. (See Picture 5.8)

Picture 5.8. Position of hip circumference measurement

Hip circumference measurement procedure

Same as for waist circumference, except for tape position.

Self-reported hip circumference

If the participant is immobile or refuses to have his/her hip circumference measured, this fact should be recorded in the data collection form. His/her self-reported hip circumference is not acceptable as a substitute.

Hip circumference exceeds the length of the tape

If the hip circumference exceeds the length of the tape, this fact together with  the maximum length of the tape (see Appendix 5.1), should be recorded in the data collection form.

5.3 Training of the measurers

All measurers should receive training before they start actual work in the field. Training should include lectures and practice measurements and should be concluded with certification (or termination of appointment) of the measurer.

During the lectures the measurement protocols should be reviewed and discussed. Possible problematic situations that might arise in the field are described and solutions for them are given. Also the quality control procedures during and after the survey are described.

Practice measurements are made under supervision and if they meet agreed upon criteria, the measurer is certified. The performance may be evaluated on the basis of

• Placement of tape
• Variability between duplicated measurements of a number of subjects.
• Comparison with repeated measurements of a number of subjects by different measurers.
• Terminal digit preference.

5.4 Quality control

5.4.1 During the survey

Quality control measures during the survey involve checking and re-calibrating of equipment and monitoring of the performance of the measurers.

The checking and re-calibrating of equipment should occur at regular device-dependent intervals. A log book of the checking and recalibrations need to be kept.

For monitoring the performance of the measurers the following information should be checked routinely for each measurer (if the data management allows this):

1. Distribution of terminal digit for
   1. weight measurement;
   2. height measurement;
   3. waist circumference measurement;
   4. hip circumference measurement.
2. Distribution of terminal digits for full kilograms for weight measurement.
3. Mean and standard deviation of 
   1. weight measurement;
   2. height measurement;
   3. waist circumference measurement;
   4. hip circumference measurement.
4. Recording of reasons for measurements that were not performed.
5. Daily work load, to avoid fatigue.

If any problems are detected they need to be discussed with the individual measurer immediately. Just letting the measurer know that he/she has problems with the measurement procedures may correct the errors. If this does not produce results and errors persist, the measurer should be retrained or dismissed.

During extended surveys, a refresher sessions for all measurers every three months is a desirable practice.

Auditors should make surprise visits to the examination sites and observe the measurers, recording the compliance with the protocol in performance evaluation forms that can later be used to review the audit with the measurers. The auditors could also act as guest participants and take part in all anthropometric measurements.

5.4.2 After the survey

After the survey it is important to check the overall quality of anthropometric measurements. The retrospective quality assessment will discover problems that may have slipped through the control measures during the survey. It is also needed to ensure that results are accurate and comparable with other studies before they can be published.

The retrospective quality assessment is made on the pooled data of all measurers and should include:

1. Item response rates for
   1. weight measurement;
   2. height;
   3. waist circumference measurement;
   4. hip circumference measurement.
2. Distribution of terminal digits for
   1. weight measurement;
   2. height measurement;
   3. waist circumference measurement;
   4. hip circumference measurement;
3. Distribution of terminal digits for full kilograms for weight measurement.

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