General Information

Reliability and Validity
Interpretation of Measurements

Patient Cooperation

Valid measurements are not possible without cooperation from the subject. Cooperation is necessary to insure the comfort and safety of the child as well as the validity of the data collected. This requires a unique relationship between the anthropometrist and the subject. Before beginning a session, the anthropometrist must establish a rapport with the subject. The anthropometrist should help the child and parent understand what is going to be done. A brief description of all the measurements and the equipment may help put both the child and parent at ease. This is especially helpful with the skinfold measurements because many children may be afraid of the skinfold calipers. The anthropometrist should not be formal, nor should he risk accurate measurements by being too relaxed. He should not react to the measurements or the values obtained. When taking the measurement, the measurer should be firm, not reluctant. People, especially children, may react negatively to an apprehensive, insecure approach. At all times, the comfort and safety of the subject should be the primary concern.

Validity and Reliability are Vital

Sources of error in anthropometric procedures can be either within-observer or between-observer in origin. Interobserver (between-observer) reliability is the ability to obtain duplicate measurements on the same subject by multiple observers (2). Interobserver errors mainly consist of differences in which each measurer performs the technique. Adopting standard techniques such as the ones in this manual and obtaining training from a well-trained observer can help eliminate interobserver unreliability (2). Intraobserver (within-observer) reliability is the ability of an observer to repeat measurements on a subject and obtain consistent values. Intraobserver errors include imperfections in the measuring instruments, the recording techniques, and the measurer's technique (2). Careful thought by the measurer and properly maintaining equipment can help reduce intraobserver unreliability. Because of their use in diagnosis and their importance in other medical decisions, all measurements should be reliable and valid. Reliability ensures that the measurements can be relied or depended upon; that is, they are reproducible using the same technique. Validity means that the measurements produce the desired results; that is, they represent the true measure of the bodily dimension in question. All measurements require the use of a standard technique which should be reproducible. If technique is compromised for any reason during a session, the measurement should not be used. The left side of the body is the accepted side to measure by convention. If the right side is measured, it should be indicated on the data collection sheet. All measurements should be taken at least twice. The average of the two should be used for clinical or research purposes. Measurement techniques are the same in adults and children, but extra attention to error should be made for children. Error is likely to be higher in children because they will not cooperate and hold a position for any extended period of time. Special considerations also need to be made for subjects with disabilities. They may have a lower level of cognition, spasticity, ambulatory problems, or language difficulties (5). All of these situations can have an effect on the measurement; therefore, care should be taken in all settings. Anthropometry involves the subject, instrument, and meas