Clinical Studies
Reliability of Length Measurements in Full-Term Neonates

https://doi.org/10.1111/j.1552-6909.1998.tb02649.xGet rights and content

Objective:

To describe and compare the intra-and interexaminer reliability of four techniques for measuring length in full-term newborns and to determine whether the different techniques yield significantly different measurements.

Design:

A descriptive study, describing the intra- and interexaminer reliability of four length measurement techniques: crown-heel, supine, paper barrier, and Neo-infantometer. The nurses were blind to their own and to the other nurse’s measurements. The order of the nurses and the order in which the measurements were obtained was randomized.

Setting:

Mothers’ rooms in a university hospital.

Participants:

Thirty-two healthy full-term newborns.

Interventions:

Length measurements using four different length techniques were obtained twice each by two experienced neonatal nurses.

Main Outcome Measures:

To measure the infra- and interexaminer reliability, the following statistics were calculated: mean absolute differences, standard deviations, technical error of measurement; percentage less than .5 and 1.0 cm, and percentage of error.

Results:

Intra- and interexaminer differences were significantly larger when examiners used the crown-heel measurement technique. Although the intra- and interexaminer reliability of length measurements obtained with the supine, paper barrier, and Neo-infantometer techniques did not differ significantly, the amount of error in these measurements was large.

Conclusions:

Measurements obtained using the crown-heel technique are significantly less reliable than measurements obtained using the supine, paper barrier, or Neo-infantometer techniques.

Section snippets

Literature Review

Reliability is defined as the ability to repeat, reproduce, or consistently obtain the same measurements under identical conditions (Engstrom, 1988, Polit and Hungler, 1995). Intraexaminer reliability is the ability of the same examiner to obtain the same or similar measurements when measurements are repeated under the same conditions. Interexaminer reliability is the ability of two or more examiners to obtain the same or similar measurements when measurements are repeated under the same

Sample and Setting

A convenience sample of 32 newborns was selected from the nursery in a large university hospital in a midwestern city in the United States. Approval from the institutional review board was obtained before data collection. Criteria for sample selection were as follows: gestational age between 37 and 42 weeks as determined by the mother’s last menstrual period or prenatal ultrasound and confirmed by clinical examination (Ballard, Novak, & Driver, 1979); absence of congenital anomalies; absence of

Procedure

Before data collection, the order of the examiners and the order in which the four length measurements were to be obtained were determined using a randomization plan. Data collection envelopes were prepared for each newborn. The tape measures and the four color-coded index cards for recording the Neo-infantometer length measurements were placed in the envelope.

When data collection was initiated, hospital records were reviewed to identify newborns who met the criteria for sample selection. If a

Analysis

Statistical analysis included statistics appropriate for describing the reliability of physical measures, such as mean absolute differences, standard deviations of the net differences, technical error of measurement, minimum and maximum differences, percentage of differences within a critical value (Engstrom, 1988, Utermohle et al., 1983), and the percentage of error (Johnson et al., 1997). Analysis was performed using Statistical Analysis System (Cary, NC) and the Statistical Package for the

Intraexaminer Reliability

The differences between the individual nurses’ length measurements obtained using the four measurement techniques are described in Table 1. Measurements obtained using the crown-heel technique had the largest mean absolute differences and percentage of error and the smallest percentage of differences less than .5 and less than 1.0 cm.

The mean absolute differences between the individual nurses’ first and second measurements obtained via the four measurement techniques were compared using

Discussion

The crown-heel measurement technique produced measurements that had significantly lower intra- and interexaminer reliability than measurements obtained by the supine, paper barrier, and Neo-infantometer techniques. This finding suggests that the amount of error in crown-heel length measurements is larger than would be acceptable for use in clinical practice and research.

The intra- and interexaminer reliability of measurements obtained using the supine, paper barrier, and Neo-infantometer

Implications for Nursing

The measurements obtained using the crown-heel technique were significantly less reliable than measurements obtained using the supine, paper barrier, and Neo-infantometer techniques. Thus, until further studies document the reliability of crown-heel measurements, clinicians should interpret any results obtained with this technique with caution and use another measurement technique.

The crown-heel measurement technique yielded a larger amount of error than any of the other techniques studied.

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