Table 3.

Target behaviour area 2, (test selection and interpretation) grouped barriers coded by the Theoretical Domains Framework and Capability, Opportunity and Motivation Behaviour framework. Detailed information about the barriers and enablers reported for each grouped barrier can be found in the Supplementary Files (Supplementary Table S4).

COM	Barriers	Example Quote (Related to the Bolded Barrier)	Enablers
C	Role clarity e.g., different craft groups undertake different roles (TDF domain: professional identity)
	Lack of clinician genetic literacy Risk of over-enthusiastic/lack of confidence in call variants	I didn’t really understand a lot of this—the genomics science stuff and then the scientist didn’t really understand because we were talking about the clinical phenotypes—which, I think, is actually really important. NGMS2	Understanding clinician and scientist sides NGMS2 Allowing evolution of roles as comfort grows NGMS14 Meetings to break down barriers NGMS8
O	Need for preparation e.g., practitioners need to research and plan in order to participate (TDF domain: environmental context and resources)
	Lack of time and effort into learning new approach	What is challenging is the variant interpretation and that’s where, I think, your average (medical specialist) is not going to have the time or interest to invest. NGMS16	Everyone is engaged and able to speak openly NGMS4
Developing corporate knowledge: the idea that everyone is collectively developing their knowledge, commonly through MDTs and through other avenues
O	Developing corporate knowledge: building relationships (TDF domain: social influences)
	Not understanding each other’s roles No meetings	I think, it would be nice to have a particular person or go-to person, that you have a good relationship with that you can just, kind of, go bounce off questions or ideas without having to even sometimes formally… maybe, a different genetic counsellor and different, it’s just a little bit hard to know where to go. NGMS2	Communication NGMS1 Regular constructive meetings NGMS8
M	Developing corporate knowledge: trust between professionals (TDF domain: emotion)
	Less trust when there are no MDTs Trust in labs	“Well what’s the turnaround time?”, “Do they trust the results from that lab?” NGMS12	Important to develop trusting relationships with genetics NGMS9 Meetings to discuss patients NGMS8 Good clinical trust permits discussion NGMS5
	Developing corporate knowledge: safety in being vulnerable (TDF domain: emotion)
	Embarrassment at not understanding the process. Lack of comfort calling variants alone	All that kind of the jargon about how relevant a variant might be, I found that was just all a bit of gobbledygook, and I, kind of, had to stop and ask, you know, at first I was a bit embarrassed because I thought everyone else knew and then I realised that the person next to me who was a clinician also had no idea what they were talking about, so it was just, kind of, yeah, and it was just good to acknowledge at the beginning that these are two different languages and how we’re going to meet in the middle. NGMS2	Getting involved NGMS12 Access to support when needed NGMS2 Positive open culture NGMS4
	Developing corporate knowledge: still learning (TDF domain: intentions)
	We’re still learning Still need support of other professionals	I’m still very much learning? Very much learning about what it all means and very much guided by—we’re very lucky here ‘cause we do have the geneticists and things, so they can help talk a little—“well this is what it means”. So I’m learning. NGMS12	Discussion promotes “automatic” learning, NGMS9

Green—opportunity; Yellow—motivation.