Inter- and intra-observer agreement of Prechtl's method on the qualitative assessment of general movements in preterm, term and young infants

Abstract

Background

Prechtl's method on the qualitative assessment of general movements (GMs) has been shown to be a good predictor of neurological outcome. There is substantial evidence that this method has good inter- and intra-observer agreement.

Aims

We wanted to find out whether this high agreement is reproducible in the clinical setting.

Study design

Reliability study (inter- and intra-observer agreement).

Subjects

Twenty video-sequences of children at the age of preterm and writhing movements (31–41 weeks postmenstrual age) and 10 video-sequences of children at the fidgety movements age (49–54 weeks postmenstrual age) were rated by five physiotherapists.

Outcome measures

Intra- and inter-observer agreements were analyzed with percentage agreement and with nominal kappa statistic with bootstrapped bias corrected 95% confidence intervals.

Results

We found fair to substantial inter-observer reliability for the six response categories (time-point 1(t1): median kappa 0.44, range 0.27 to 0.59, time-point 2 (t2): median kappa 0.55, range 0.41 to 0.77) and fair to almost perfect for the normal/abnormal ratings (t1: median kappa 0.53, range 0.29 to 0.61, t2: median kappa 0.63, range 0.29 to 0.85). There was statistically significant improvement from t1 to t2 for the six response categories. The intra-observer reliability for the 9-week interval was moderate to almost perfect (median kappa 0.68, range 0.41 to 0.86).

Conclusions

We were not able to exactly reproduce the generally very good results. In our clinical setting now videos are evaluated by at least two trained therapists and the results are discussed, if necessary, to reach a consensus.

Introduction

Preterm and high-risk infants (e.g., low birth weight) have a higher risk of an abnormal neuro-developmental outcome [1], [2]. Early detection of motor impairments is important for a timely start of intervention programs [3], [4], [5]. Prechtl's method on the qualitative assessment of general movements (GMs) has proven to be an objective, reliable and valid diagnostic tool for early recognition of brain dysfunction [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]. It was developed by Prechtl and co-workers. They founded in 1997 the General Movements Trust (GM Trust) in order to promote Prechtl's method. Since then the GM assessment is increasingly and widely employed in clinical routine and supported by the licensed instructors of GM Trust, who educate physiotherapists and physicians in their training courses and educations concerning the detection of movement patterns [16]. Human fetuses, preterm, term and young infants during the first months of life, have a repertoire of distinct centrally generated movement patterns. Among these different spontaneous movement patterns, the GMs are the most effective to evaluate the integrity of the young nervous system [17]. They can be observed from 9 weeks postmenstrual age (PMA) up until 5 months post-term age (PTA) [18]. The quality of these movements changes if the nervous system is impaired [19]. GMs are age-specific. Before term age they are called fetal and preterm GMs, around term age writhing movements and from 9 weeks post-term age onwards fidgety movements. Preterm and writhing GMs involve the whole body and they are characterized by the variable sequence of arm, leg, neck and trunk movements. Their intensity, force and speed begin and end gradually. Frequent changes in direction and rotations along the axis of the limbs make the movements fluent, elegant, complex and variable [16]. Abnormal patterns of GMs during the preterm and writhing periods are poor repertoire (PR), cramped synchronized (CS) and chaotic (Ch). The character of GMs changes to fidgety movements (FMs) around 9 weeks post-term. FMs are small, circular movements of moderate speed and variable acceleration of neck, trunk and limbs in all directions. Abnormal patterns of GMs during the fidgety movement period are rated as absent (F−) or abnormal (AF) fidgety movements. If the normal quality of GMs has changed this is a reliable indicator of brain dysfunction. The quality of GMs is assessed by means of video recordings and is based on the visual Gestalt perception of the observer [13]. Gestalt effect refers to the visual recognition of figures and whole forms instead of a collection of details [20]. In the physiotherapy unit of the Children's Hospital, Bern University Hospital, GM is used for standard assessment of preterms born before the 28th week of gestation, after severe asphyxia or with neurological abnormality in development. In the clinical field it is very important to be able to apply a method that is valid, reliable, non-invasive, low-cost, non-time-consuming and highly predictive for a better identification of infants that can profit from early intervention services [3], [4], [21], [22]. It is claimed that the assessment can be reliably performed by trained physiotherapists. There is substantial evidence that Prechtl's method has good inter- and intra-observer agreement [12], [13], [14], [15], [23], [24]. But most studies have been accomplished by members of the GM Trust who are highly skilled in evaluating GMs. We wanted to find out what is the reliability of the inter- and intra-observer agreement in a clinical setting. The specific research questions were (a) whether the inter-observer agreement is acceptably high (at least classified as substantial, median kappa > 0.6) between five experienced physiotherapists, (b) whether the intra-observer reliability is acceptably high (median kappa > 0.6) between two rating sessions with an interval of 9 weeks, and (c) whether there is a difference in the agreement if the videos are classified using the six different GM categories (nominal response categories) or only normal/abnormal (dichotomous).