Development, reliability and validity of infectious disease specialist Nurse’s Core competence scale

In the first stage, through literature review, theoretical analysis and qualitative interview, we constructed the first draft of the core competence evaluation index system of infectious disease specialist nurses which was composed of 6 primary indicators, 17 secondary indicators and 48 tertiary indicators, and adopted the 5-point scoring method. The primary indicators were Nursing Abilities for infectious diseases, Infection Prevention and Control Abilities, Responsiveness to Infectious Diseases, Professional Development Abilities, Communication and Management Abilities and Professionalism and Humanistic Accomplishment. Then, we invited experts in the field of specialized medical treatment and nurses of infectious diseases for Delphi consultation [16]. The inclusion criteria of consultation experts were as follows: (a) has engaged in clinical nursing or medical work of infectious diseases at least 15 years; (b) has intermediate level title or above; (c) has bachelor degree or above; (d) voluntarily participates in the research. Through Delphi expert consultation, the index system was scored and modified, and the judgment coefficient, authority coefficient and familiarity degree of Delphi experts were 0.933, 0.923 and 0.913 respectively. The core competence index system of infectious disease specialist nurses was finally established, which included 6 primary indicators, 16 secondary indicators and 47 tertiary indicators [17].

Then, through the panel meeting, we compiled the index system into ‘Infectious Disease Specialist Nurse’s Core Competence’ pretest scale which included 47 items. Before the formal investigation, the preliminary scale was distributed to 5 head nurses to test the level of item comprehension, appropriateness of the font size, survey structure and item length. The evaluation of the pre-test scale by five head nurses had good internal consistency, which was 0.851, indicating that it can be used for formal investigation. In the first round of investigation, 40 head nurses from the infectious diseases department were invited to evaluate the core competence of 516 infectious disease specialist nurses through the pre-test scale. Discrete trend, critical ratio, correlation coefficient, Cronbach’s α coefficient and factor analysis were adopted for item analysis. Through item analysis and exploratory factor analysis, we filtered the items and drafted a preliminary scale, which was composed of 5 factors and 36 items. And the scale was basically consistent with the index system of core competence of infectious disease specialist nurses constructed in the previous study.

In the third stage, we conducted the second round of questionnaire survey. The core competence of 497 infectious disease specialist nurses was evaluated by 42 head nurses with the first draft of Infectious Disease Specialist Nurse’s Core Competence Scale. We took a series of measures including item analysis, reliability test and validity test to filter the scale items and re-explore and verify the structure of the scale. The methods of item analysis were the same as above. Reliability analysis included test-retest reliability, internal consistency and split-half reliability. Validity analysis included content validity and structure validity. In the second round of questionnaire survey, about 10% of the subjects were randomly remarked, and the questionnaire was sent out again 2 weeks later to measure the test-retest reliability. Finally, a scale with high reliability and validity was formed, including 5 dimensions and 34 items.

The inclusion criteria of head nurses and senior nurses: (a) have engaged in infectious disease nursing for more than 10 years; (b) have nurse in charge title or above; (c) have good communication and expression skills; (d) voluntarily participate in research. The inclusion criteria of infectious disease specialist nurses: (a) have engaged in infectious disease nursing for more than 5 years; (b) have participated in infectious disease specialist nurse training and got the certificate.

The sample size was determined by the general rule that factor analytic procedure requires a minimum of five respondents per item, but a larger sample is desirable [18, 19]. In our study, ten respondents per item were required to ensure the accuracy of factor analysis. Therefore, during the two rounds of questionnaire investigations, head nurses of infectious diseases department were selected by convenient sampling method to evaluate the core competence of infectious disease specialist nurses.

Data were analyzed by SPSS 23.0 and Mplus 8.3 software.

For item analysis, items were screened with the Classical Test Theory [20] which included discrete trend method, critical ratio method, correlation coefficient method, Cronbach’s α coefficient method and factor analysis method. The standard deviation of item scores represented the degree of dispersion. When SD < 0.85, it indicated that the item was not able to distinguish and was to be deleted. The total score of the scale was ranked from high to low, and the relationship between the high-score group (the first 27%) and the low-score group (the last 27%) was analyzed to judge the discrimination of the scale. It was the same to the factor loading. If the total score was less than 0.4, the item needs to be deleted. If Cronbach’s α coefficient became larger after deleting the item, it indicated that the item would lower the internal consistency of the scale and should be deleted [21].

Reliability analysis referred to the consistency of the results of repeated measurement of the same object by the same method [22, 23]. For reliability analysis, we used Cronbach’s α coefficient, split-half reliability and test-retest reliability. Cronbach’s α coefficient was used to evaluate the internal consistency reliability of the scale. The scale was divided into two parts according to the order of oddness and evenness, and the correlation between them was to calculate the split-half reliability. Two weeks later, we would conduct a test-retest on the nurses marked before, and measure the test-retest reliability.

Validity analysis referred to the analysis of the accuracy of the scale [24, 25]. For validity analysis, we conducted content validity analysis and structure analysis. The validity of the content was evaluated by Delphi experts’ scores which included the content validity index of the items (I-CVI) and content validity index of the scale (S-CVI). The structure analysis contained exploratory factor analysis and confirmatory factor analysis. Index value standard: The Kaiser-Meyer-Olkin (KMO) > 0.6, χ2/df < 3, Root mean square error approximation (RMSEA) < 0.08, Comparative fit index (CFI) > 0.90, Tucker-Lewis index (TLI) > 0.90, Standard root mean-square residual (SRMR) < 0.80 [26].

Research was approved by the ethics committee of Tangdu Hospital of Fourth Military Military Medical University, China (Number TDLL2019-09-13). Informed consent was obtained from all participants included in the study and they could withdraw from the study at any time for any reason. Moreover, they were assured that the questionnaires would only be used for research.

From January to March 2021, 540 questionnaires were distributed in the first round of survey, and 516 were effectively recovered, with an effective recovery rate of 95.56%. The average age of head nurses was (42.15 ± 5.57), and the average number of years of nursing infectious diseases was (18.75 ± 6.03). The average age of infectious disease specialist nurses was (31.02 ± 5.17), and the average number of years engaged in infectious disease nursing was (9.29 ± 4.23). From May to July 2021, the second round of questionnaire survey was conducted. A total of 517 questionnaires were distributed and 497 valid questionnaires were recovered, with an effective recovery rate of 96.13%. The average age of head nurses was (41.60 ± 4.54), and the years of nursing infectious diseases were (17.36 ± 4.76). The average age of infectious disease specialist nurses was (32.17 ± 5.77), and the number of years engaged in infectious disease nursing was (9.02 ± 3.78). Other demographic data are shown in Table 1.

Discrimination analysis was conducted on the evaluation scale of core competence of infectious disease specialist nurses. T-test and analysis of variance were used to compare the core competence and scores of 5 dimensions of infectious disease specialist nurses with different demographic characteristics. The research results are shown in Table 7. The results showed that there were significant differences in the scores of core competence and its five dimensions among infectious disease specialist nurses of different ages, working years in infectious diseases, titles, educational background, marital status and wages (all P < 0.05).

Among all present researches, there was no tool targeted at evaluating the infectious disease specialist nurse’s core competence. This study is of great significance to some degree since this study aims at establishing an effective system targeted at evaluating the infectious disease specialist nurse’s core competence, which can provide reference to the training and assessment of the infectious disease specialist nurses and improve the quality of infectious disease nursing care. And the study is innovative because the Infectious Disease Specialist Nurse’s Core Competence Scale compiled by the research team under the theoretical guidance framework of the Core Competence Evaluation Index System of Infectious Disease Nurses constructed in the early stage fills the gap in the field of the core competence evaluation of the infectious disease specialist nurses.

The scale was under the guidance of Core Competence Theory [27] and designed in combination with the characteristics of the infectious diseases (Ma & Cao, 2018; Wu et al., 2020) and the actual situation of the infectious diseases [28]. In the process of constructing the scale, every dimension was endowed with a mission for infectious disease specialist nurses to fulfill. And the missions required the nurses to be able to give lectures, do scientific researches and undertake administrative work so as to advance professional development; to be able to strictly implement infection prevention and control; to be armed with solid theoretical knowledge and operational skills so as to undertake the nursing work of the infectious disease patients; to able to respect the infectious disease patients and to be able to respond to Emergency Infectious Diseases. The scale was designed for scientifically and effectively evaluating the core competence of the infectious disease nurses and providing measurement tool for carrying out clinical infectious disease nursing care and improving the specialist nurses’ abilities. The higher the score of the scale the nurse got, the higher the level of the nurse’s core competence was. In this way, the scale was of practicability.

The Infectious Disease Specialist Nurse’s Core Competence Scale, featured as high reliability and validity, was finally established with 5 factors and 34 items after preliminary evaluation and exploration in the first round and re-evaluation in the second round. The cumulative explanatory variance of the five factors was 75.569%, indicating that the five factors could explain the difference in core competence of infectious diseases specialist nurses to the extent of 75.569%. The scale had a clear structure and was roughly consistent with the index system constructed in the first part, which confirmed the rationality of the design structure. Through a series of methods such as a large number of literature review, theoretical analysis, qualitative interviews, expert correspondence, etc., the comprehensive consideration of the core competence of infectious disease specialist nurses was transformed into an evaluation tool, which had a certain degree of scientificity.

On the basis of reliability and validity evaluation, the differences of core competence and its dimension scores of infectious disease specialist nurses in different demographic characteristics were compared, and the influencing factors of core competence were preliminarily explored. The core competence of infectious disease specialist nurses aged 31–40 was higher than that of low and high age group; the core competence of specialist nurses who have worked in infectious disease nursing for 11–20 years were higher than those who have worked for less than 10 years and more than 20 years; the core competence of nurse in charge was higher than that of the nurse or the deputy chief nurse or above; specialist nurses with middle salary level had the highest score in core competence. The nurse in charge has longer working years and accumulated a lot of clinical experience in infectious disease nursing than younger nurse. At the same time, compared with older nurses, the nurse in charge was the core backbone of the Department and was mainly responsible for the nursing and management of infectious diseases, so the level of core competence was the highest. The core competence score of nurses with bachelor degree was higher, because they have received a higher education level and can better master clinical skills and improve clinical nursing ability [29]. Zuriguel-p é rez et al. [30] found that highly educated nurses often have better critical thinking in nursing work, which is also an important aspect of core competence. The core competence of married specialist nurses was higher than that of unmarried or divorced nurses, which may be related to the family support from relatives for nurses’ work. Especially the nurses in the Department of infectious diseases are facing great work pressure and the risk of occupational exposure [31]. Family support and recognition are the driving force of their work, which can make them better put into work [32, 33].

In this study, cross group measurement invariance analysis on the scale was not done. So it was not clear whether there were differences in the application in different groups with different characteristic [34]. And In the next step, we will analyze the invariance of cross group measurement to figure out the differences in the application in different groups. Besides, we will introduce Generalizability Theory (GT) and apply it in the re-evaluation of the scale so that we can further verify and improve the reliability and validity of the scale [35].