Aim of the tool validation study

To establish the diagnostic accuracy and utility of the BESST as a swallow screening tool by:

1. Determining the intra- and inter-rater reliability of the BESST within, and between nurses, and the gold standard SLT bedside clinical assessment. 2. Determining the sensitivity, specificity, the positive and negative predictive

values of BESST in identifying aspiration in patients following a stroke, and the efficiency of the BESST when undertaken by a nurse not trained in dysphagia assessment compared with the gold standard SLT bedside clinical assessment. 3. Exploration of the clinical determinants of aspiration reported by the nurses. 4. Identifying how the management options from the BESST compare with those

made by the gold standard SLT bedside clinical assessment.

Ethical Approval

A notice of substantial amendments was applied for, and was approved (Appendix 29), from the relevant Research Ethics Committee; with amendments regarding the BESST format, procedure and sample size.

Subjects

Consecutive stroke patients admitted to an acute stroke unit in a large teaching hospital from November 2005 to April 2006 were identified. All patients were

considered for inclusion in the study. Patients were excluded if they were transferred to the rehabilitation unit at another site, or home, prior to contact with the researcher.

Sample size

From previous pilot work, it was found that the proportion of “successes” for the tool was between 0.150 and 0.174. Successes were defined as complete agreement with the SLT when rating for nil by mouth, modified, or normal diet. Assuming that the true value of the kappa is 0.6, with a two-sided 95% confidence interval for the kappa to extend 0.2 from the observed value of kappa, and the proportion of successes to be 0.174, we would need a sample size of 110 patients. Should the proportion of successes be 0.150, a sample size of 124 patients would be required. To achieve a sample of 110 to 124 patients, 140 patients would need to be recruited to allow for attrition.

Procedure

Each participant was initially approached by the research nurse and invited to

participate in the study. They were given an information sheet regarding the study and were given 12 hours to consider their participation. Written consent was obtained from the participant, or relative assent was obtained from their next of kin if the participant had cognitive or language difficulties and were unable to personally give informed consent. Witnessed consent was obtained where the participant was able to indicate agreement to take part in the study but was unable to physically sign the form.

Once consent or assent had been obtained, the researcher recorded details of the patient‟s age, sex, date of stroke onset, date of admission, pre-existing dysphagia, pre- existing nutrition/hydration status and stroke type (Appendix 30).

Each patient was assessed on two consecutive days by three raters: the SLT, a nurse from the wards (N1) and a research nurse (N2). The SLT and N2 were the same raters used in the feasibility study. The general nurse, not experienced in nursing stroke patients was new to the study.

The nurses were asked to follow the instructions on how to use the tool, available on the back of the tool. Nurse 2 had limited experience of undertaking the pilot screen, that is they had used the screen on 12 purposefully selected stroke patients, but neither nurse had received targeted training using the BESST, nor experience of assessing dysphagia in patients with neurological problems as part of their day to day work. The nurses were therefore required to follow the BESST without drawing on previous experience. All raters were asked to record contemporaneous reasons for their decisions, as well as to record any bias that may have influenced their

management decision, e.g. drinks at bedside cabinets or clinical dilemmas. For example, whether or not to continue assessment if the patient coughed on swallowing water.

Patients were rated for swallowing problems at their bedside by the specialist SLT, who used his clinical judgement (gold standard assessment), and by the two nurses who used the BESST. Each patient received contiguous but independent swallow screens and the raters‟ order of assessment was randomised to minimise the effects of swallow fatigue. As described previously on page 126, the two nurses‟ assessments and the assessment by the SLT meant that each patient was assessed three times, over a 30

minute period on average, on each of the 2 days. All raters were blind to the results of each others‟ ratings.

To minimise the effects of fluctuation in the patient‟s medical state for the intra-rater reliability studies, undertaken on day 2, the SLT identified changes in patients‟ status by discussion with nursing staff and examination of the medical notes and nursing cardex prior to the series of randomised SLT assessment and BESST screens. Any patients who demonstrably deteriorated or improved had their data excluded from the assessment of intra-rater reliability.

For patients included in the study, the results of assessments were not used to inform clinical care.

Gold Standard assessment

The gold standard assessment was the SLT‟s normal assessment and clinical care, which typically included a case history; discussion with the patient, relatives and staff; lunchtime observations; cervical auscultation; pulse oximetry and laryngeal palpation. The laryngeal palpation includes four finger assessment using different consistencies of 2-3 spoons of water (average capacity 7 ml/spoon), bolus swallows from a cup (average bolus 20 ml), sequential drinking from a cup, and assessing the person‟s ability to swallow yoghurt consistency and biscuit. The SLT confirmed that the clinical determinants of aspiration included in the gold standard assessment typically include absent swallow reflex, coughing, wet voice, wet breath sounds, and repetitive clearing swallows. Patients are observed for abnormal responses and reflexes that are

indicative of silent aspiration e.g. hiccups and yawning. Further testing includes posture modification, different bolus consistencies and compensatory safe swallow strategies. The SLT reported that their management decision regarding the safest consistency to be taken orally is based on some, or all, of their clinical assessment described above, with eclectic use of different assessments and observations dependant on the patient‟s clinical presentation. This is reflective of clinical practice within the hospital setting (McCullough et al., 1999).

Bedside Swallow Screening Tool (BESST)

Stage 1 Pre-screening

The BESST (Figure 8.1 and Figure 8.2) includes a pre-screening where clinicians identify patients at a high risk of aspiration. This pre-screening includes:

 conscious level (unconscious; stuporosed; rousable; alert)

 trunk control (no trunk control; can be supported upright; has trunk control) head control (no head control; can be supported; has head control)

 voice quality (wet gargly voice; normal voice)

 ability to perform a voluntary cough on request („yes‟ or „no‟). The BESST dictates that patients identified as at high risk of aspiration i.e.

unconscious; stuporosed; no trunk or head control; has a wet gargly voice; and are unable to perform a voluntary cough, should be placed nil by mouth and referred

immediately for a more specialist dysphagia assessment. The BESST also dictates that patients who have a pre-admission history of recurrent chest infections should be referred for a specialist dysphagia assessment subsequent to screening with the BESST (regardless of their BESST score). Once the pre-screening has been

completed, if it is safe to continue, the direct assessment where swallowing is tested is performed.