Predicci´on de desplazamiento por lateral spreading

This section reports what the recruitment process entailed for potential experimental groups’

participants, what the testing involved and what information was obtained during the testing

process for the database that was subsequently used for statistical analysis.

3.4.1 Patient recruitment process

Potential CKD (not receiving haemodialysis) participants were identified from clinic lists up

to three months prior to their appointment. The participant information sheets were posted to

eligible individuals at least four weeks prior to their clinic appointment. This information

sheet is shown in Appendix 3. Two weeks before the clinic, potential participants were

contacted via telephone to establish interest in participation of the study. Understanding of

what the study entailed was assessed over the telephone and any questions about what the

testing involved were answered. Individuals were also informed that if they subsequently

decided against participation on the day of their appointment this would not affect their healthcare. Outpatient testing was carried out before or after individuals’ appointments in the

outpatient department. Testing began only after questions regarding the study were answered,

it was ascertained they had a good understanding of what the study involved and voluntary

and informed consent was obtained. The consent form signifying that participants’ agreed to

participate in the study is shown in Appendix 4. The order the tests were administered was as

follows: Pro-saccade paradigm, anti-saccade paradigm, ACE-R, NART, digit span, spatial

span, Stroop task, and HADS. This ordering of test administration was the same for control

participants also.

Participants receiving dialysis were approached during their dialysis session and given the

participant information sheet (Appendix 3) to consider. A two-week period was then allowed

so people could carefully consider their potential participation in the study. Individuals given

information sheets were asked via telephone or in person if they wanted to participate. All

potential participants were assured that deciding not to participate would not affect their

clinical care. Those who voluntarily gave informed consent were tested once it was

established that they had a good understanding of what the study involved. There is

conflicting evidence in the existing literature concerning the impact timing of dialysis sessions

has upon optimal cognitive performance.(91, 149, 150) _{However, there is no consensus between}

authors as to when cognitive performance is at its worst so testing was carried out during and

after dialysis sessions. Both dialysis units were quiet so there was no interruption to the

neuropsychological battery. The oculomotor tasks were carried out in a separate room within

the dialysis unit after participants’ haemodialysis sessions.

Initially, recruitment of haemodialysis patients occurred from one dialysis centre. However,

due to low participation rate a second site was added. This was reflective of the nature of

ESRD requiring HD; most people in this subgroup had numerous co-morbidities meaning

they did not want to participate. Additionally, a majority of patients receiving in-centre HD

met one or more conditions of the exclusion criteria (see Participants section). For example,

which was being treated with pharmacotherapy, or chronic pain associated with uraemia that

required opioid analgesics.

3.4.2 Control recruitment process

Information sheets outlining what the study entailed and why it was being carried out were

circulated within the Continued Learners group from Lancaster University, and among potential CKD participants’ partners/spouses. This information provided contact details of the

authors, so potential participants were given the opportunity to ask questions regarding the

study via telephone or e-mail/ arrange a suitable time to participate. Testing was then carried

out at the Lancaster University Psychology department, or the outpatient department of the

aforementioned hospitals once it was ascertained that participants had a good understanding of

what was involved in the study and subsequent voluntary and informed consent was given.

Participants were also advised that they could withdraw consent at any stage during testing.

Those who travelled to participate were offered £10 towards travel costs so no participant

would incur financial loss.

3.4.3 Database

The following results were recorded and compiled to make a comprehensive database for

statistical analyses after testing. In addition to demographic information and test results, the

blood test results of CKD participants were recorded. The GFR reading for participants with stage 1 and 2 CKD was given as ‘GFR >60 ml/min per 1.73m2_{, in one NHS trust, causing less}

accurate readings. However, the second trust used for recruitment gave the precise eGFR

readings for those in early CKD stages. For all participants with later stages of CKD a precise

GFR reading was given. The eGFR of CKD and HD participants was obtained within two

literature; previous studies mostly obtained blood results that were recorded from samples

taken one or two months prior to cognitive testing.(15, 79, 94)

Information obtained from all participants:

 Demographic Information: o Age

o Gender

o Years of Education

o Smoking status

o Weekly alcohol intake

 Medical Information:

o Comorbidities

o Medication use

 Oculomotor task parameters:

o Percentage of anti-saccade errors

o Percentage of corrected anti-saccade errors

 Neuropsychological battery:

o ACE-R score (maximum score of 100)

o Time in seconds taken to complete the Stroop task

o Number of errors in Stroop task

o Number of corrected errors in Stroop task

o Individual item score of 14 items in HADS (0-3)

o Forward and reverse digit span scores (maximum score of 16 or 14,

respectively)

o Forward and reverse spatial span scores (maximum score of 16 for

each)

Obtained only from CKD participants:

 Aetiological cause of CKD  Dialysis status

 Blood results:

o Estimated GFR (eGFR)

Obtained only from haemodialysis patients:

 Number of months receiving haemodialysis