A total of 182 participants completed the survey (95% response rate) ranging from 91% to 100% across centers. In network analysis, survey non-respondents are still considered as members in the full network because respondents are still able to nominate non-respondents. Therefore, our total network contained 192 members. Characteristics of ISC3 network members are reported in Table 1. Non-respondents (n=10) were excluded from counts/totals where participant characteristic information is necessary. Most participants reported their primary discipline as public health (54.4%) or medicine (24.2%). More than two-thirds (69.8%) of network members reported ten or more years of experience in their field. The most prevalent network roles were faculty (60.4%) and center staff (23.6%). The largest proportion of network members reported intermediate expertise in IS (41.8%), followed by beginner (35.2%) and advanced (23.1%) expertise. Most members identified as female (68.7%) and white (78.7%).
With all collaboration activities combined, the ISC3 network included 192 members with a total of 2480 collaboration ties, of which members had a median 22 connections (Table 2). Figure 1 shows the network for all collaboration activities combined and Figure 2 displays the network for each separate collaboration activity. The greatest number of ties were reported in planning/conducting research (1470 ties; median 15 ties/member) and the fewest ties were reported in practice/policy dissemination (284 ties; median 2 ties/member). The ISC3 density for all collaboration activities was 13.5%. Across the different collaboration types, the most and least densely connected network activities were planning/conducting research (8.2%) and practice/policy dissemination (2.6%), respectively. The practice/policy dissemination network was the smallest network with just 143 of the 192 ISC3 network members represented whereas the other networks ranged from 173-190 members.
The overall ISC3 network was fairly decentralized (degree centralization=0.33 and betweenness centralization=0.07; Table 2) consistent with Figure 1’s basic linked local networks shape (no strong central node or group of nodes). For separate activities, capacity building and product development had the highest degree centralization (0.23 and 0.21, respectively) compared to other collaboration activities, which ranged from 0.12 to 0.17, suggesting influential positions for some members in these networks (“hub and spoke” network structure). Scientific dissemination and practice/policy dissemination networks had the highest betweenness centralization (0.23 and 0.20, respectively), suggesting some members may be closer to each other and/or are more easily connected or reached. As more connections “pass” through these central members, their removal would result in high number of isolates.
Overall, the ISC3’s transitivity (0.47) suggests heightened probability of triangles in the network, though variation exists across collaboration types. Planning/conducting research had the highest transitivity measure (0.56) compared to all other collaboration networks (transitivity range: 0.33 to 0.37), suggesting that two investigators that are collaborating with the same investigator are likely to also be collaborating with each other.
One-third of all collaboration ties (33.0%) occurred between members from different centers. For specific collaboration activities, we observed the largest portion of cross-center collaboration in product development (48.1%), which includes involvement with cross-center work groups. Collaborating on practice/policy dissemination and planning/conducting research mostly occurred within members’ respective centers (6.0% and 11.7% cross-center ties, respectively). Network members had a median 17 connections within their own center and 7 connections from other centers across all activities.
There were no isolates for the all collaboration activities network because our overall network was derived from having at least one collaboration activity reported. Notably, practice/policy dissemination and product development were the two activity networks with the largest number of isolates, 22% and 10% of the total number of network members (n=43 and n=19, respectively). Descriptive analysis on isolates from these two activity networks showed that half of ISC3 trainees (n=6) were not connected in product development whereas other roles represented 0-33% of isolates. For practice/policy dissemination, 44.4% (n=8) of those with less than 5 years of experience in their field were not collaborating, compared to those categories with more experience (range 16.1%-16.9%). NCI staff (n=5) and trainees (n=4) also made up larger portions of isolates in the policy/practice dissemination network (45.5% and 33.3%, respectively).
Connectivity by Participant Characteristics
In all collaboration activities combined, the number of connections (degree) varied significantly across ISC3 roles (c2=10.59(4), p=0.032), IS expertise level (c2=34.42(2), p=<0.001), and racial/ethnic background (c2=13.14(4), p=0.011) (Table 1). Among groups with the highest median degree were those with advanced IS expertise (39.5 (range: 12-89) ties), NCI staff (28 (6-65) ties), and Hispanic or Latino network members (32 (24-45) ties). Median degree did not vary significantly across discipline, years of experience, or gender identity for all activities combined.
Network members had a median of 15 collaborations (range 1-48) in planning/conducting research which varied significantly across IS expertise level (c2=15.74(2), p=<0.001), network role (c2= 27.94(4), p=<0.001), and race/ethnicity categories (c2=25.52(4), p=<0.001). Those with advanced expertise in IS reported the highest number of collaborations (Mdn 20: range 5-48). Other groups with the highest median number of connections were faculty and staff (Mdn 17: range 5-48 and Mdn 17: range 4-29), and Hispanic or Latino respondents.
Median degree for capacity building activities was 10 (range 1-58) and varied across IS expertise level (c2=34.17(2), p=<0.001) and ISC3 role (c2=11.97(4), p=0.018). Members with advanced IS expertise (Mdn 24: range 4-58) and NCI staff (Mdn 20: range 6-53) had the most connections. The least connected members were staff (Mdn 7: range 1-48) and those with beginner IS expertise (Mdn 7: range 1-49).
The product development network members had a median of 6 collaborations (range 1-45), which varied significantly across years of experience in field (c2=17.81(3), p=<0.001), role (c2=10.06(4), p=0.039), and IS expertise level (c2= 20.21(2), p=<0.001). Across years of experience categories, those with more than 15 years of experience in their field were the most connected (Mdn 10: range 1-45). For role, NCI staff (Mdn 7.5: range 3-45) and faculty (Mdn 7.5: range 1-42) had the same median number of connections. And across IS expertise, advanced members had the largest number of connections in activities to develop products (Mdn 9: range 1-45).
Network members had a median of 5 collaborations (range 1-30) in scientific dissemination activities. The number of collaborations in this activity network varied significantly across years of experience in the field (c2=12.40(3), p=0.006), role (c2=11.31(4), p=0.023), IS expertise (c2=40.80(2), p=<0.001), and racial/ethnic background (c2=22.50(4), p=<0.001). The most connected members were Hispanic or Latino (Mdn 16: range 4-19) and advanced IS experts (Mdn: 12: range 1-30).
Practice/policy dissemination connections varied significantly across discipline (c2=7.20(2), p=0.027) categories and role (c2=12.10(4), p = 0.017) and had an overall median degree of 2 (range 1-22). Across disciplines, public health and medicine both had a median of 3 collaborations (range 1-21 and 1-22, respectively) and other disciplines had slightly less (Mdn 2: range 1-10). Across roles, staff had the highest median number of connections (Mdn 4: range 1-22), followed by faculty (Mdn 2: 1-21), trainees (Mdn 2: range 1-5), other (Mdn 1: range 1-6), and NCI staff (Mdn 1: range 1-2).
Full results from our sensitivity analysis are available in Additional File 3, in which we adjusted for extreme outdegree levels. For example, for all collaboration activities combined, the number of ties was reduced from 2480 to 2419 as a result of removing outgoing unreciprocated ties from “outlier” respondents (n=4) with an outdegree more than Q3+1.5*IQR. Network- and node-level characteristics were generally similar across the full and reduced datasets for each type of collaboration, however we note the following exceptions: (1) when comparing across roles in ISC3, we observed nonsignificant differences in the number of connections for product development and practice/policy dissemination; (2) we observed a significant difference in the number of practice/policy dissemination connections by IS expertise, with the highest median number of connections among those reporting advanced expertise (Mdn 2.5; range 1-7) followed by those with beginner (Mdn 2; range: 1-9) and intermediate (Mdn 1; range: 1-8) expertise; (3) there were fewer median capacity building ties among Black or African American respondents (Mdn 11 in the full analysis vs. 6 in the sensitivity analysis); and (4) a large increase in the number of practice/policy dissemination isolates (n=43 in full analysis; n=65 in sensitivity analysis).