In nursing, interpersonal skills may be predictors of satisfaction since they are a relevant component of nurses' skills ¹. Soft skills in nursing care are important attributes that may be even more relevant than care, the technical component of user satisfaction ². Warmth is an important attribute in health care that is also a relevant factor and a decoder of patients' communication ³. However, this attribute has been little explored in health and nursing care. Warmth holds an incredibly special place in life because it works throughout the entire spectrum of human experience. A positive family context, characterized by warm relationships promotes the positive development of children towards adolescence ⁴. Warmth also helps us be healthy human beings on many distinct levels ⁵.

Warm behaviors have strong impacts on the measurement of users' satisfaction ⁶. For patients, kindness, smiles, affection, and tenderness have greater relevance than the technical component of care ⁷. As an example, respect, supportiveness, communication, and faithfulness are among the most frequently identified personality traits of "good nurses" ².

A nurse's warmth and professional competences are fundamental aspects perceived by the patient with a compensatory association between them. Both dimensions are essential in social judgment and show that the appreciation in either of them influences the way a person judges another ⁸. Therefore, warmth and competence predict an increase in helping intentions ⁹.

When studying warmth measurement in the nursing practice, no instruments were found. Despite the relevance of this important dimension, there is not enough evidence to highlight this value in nursing care nor a consistent way for its measurement.

With the above in mind, the objective of this study was to construct and validate the Nursing Warmth Scale (NWS) through the development of a standardized measurement of nursing professionals' warmth, from the perspective of patients, and identify the behaviors and factors associated with this concept.

This is a methodological and psychometric study on the construction of a psychosocial construct measurement scale using the psychometric reference.

A study was conducted to build and validate the NWS ¹⁰. The psychosocial construct was formulated using the psychometric test reference ¹¹ developed in three phases: theoretical, empirical, and analytical ¹². A theoretical review and interviews with patients and professionals were included, as well as an assessment with a panel of 10 judges ¹³.

The conducted procedures included an integrative review, following the recommendations for this type of studies ¹⁴ included in works previously published by the authors ¹⁵. Additionally, interviews with patients and nurses were performed with the aim of broadening the understanding of concepts and behaviors around the feeling of warmth.

The authors developed the construction of items, during a first phase, with the results of an integrative review that consolidated the construct "Nursing-warmth" and a set of variables related to this concept ¹⁵, and with the information provided by the qualitative study developed to evaluate the latent variable and increase the pool of items. The construct of warmth is then understood as "The ability to establish and maintain a close host relationship that demonstrates tenderness, trust, the affection, and love, through both verbal and nonverbal behaviors, in such a way that it means a pleasant experience for the other person" (15, p. 106). After the formulation of the construct, warmth-related behaviors were identified and then grouped into 2 major categories: 70 verbal and 23 non-verbal behaviors.

At this stage, interviews were conducted with patients and nurses from medical units at a public hospital and private clinic, inquiring about behaviors mentally associated with warmth. Twenty-three patients with 3 days of hospitalization and 25 nurses were interviewed. The results about related behaviors derived from the analysis of the interviews ¹⁶ were incorporated into those derived from the theoretical phase, resulting in a total of 154 items.

The criteria used for reducing items from the scale was to remove those that appeared more than once. In cases where items had both negative and affirmative statements, the affirmative item was chosen. As a result, the number of items was reduced from 154 to 136.

Content validation was performed with the help of 10 expert judges, following the approaches by Mary Lynn and other authors ¹⁷. The panel was selected based on inclusion criteria, which considered experts' educational background and experience in different disciplines. Finally, six nurses, two psychologists, a civil engineer, and a social worker were selected, all of them with expertise in user satisfaction.

The group of experts performed the semantic, grammatical, and syntactic equivalence analysis of items and provided recommendations for a better understanding of these elements ¹⁷. Items were evaluated using an instrument designed for this phase of the process, which assessed their relevance, pertinence, clarity, and essentiality.

The scores assigned to each category were determined, ensuring the representation of the definitions and semantics in Spanish for each extreme of the scale. The criteria no warmth to absolute warmth was used.

The harmonization of items and standardization of the instrument was conducted in a pre-testing phase, which included a pilot test with a sample of 25 patients to check item comprehension and compliance and to collect suggestions. Only patients with 3 days or more of hospitalization were included in the sample.

The objectives of building and validating the NWS from the perspective of patients and identifying behaviors associated with warmth were fully achieved. In doing so, this study fills an existing gap regarding the meaning of warmth in nursing, since this feeling brings together interpersonal nursing skills that strongly affect patients' perceptions regarding the care experience ^1,2. Interpersonal skills have immense value in building bonds with the patient, with warmth or a human tone, being a desirable attribute of nurses in providing humane and safe care ²⁷.

The "nurse warmth" construct and the items that comprise it were initially generated from a literature review, achieving a methodological integration of the concept and its dimensions. The attributes of nurse warmth that have been defined in the current literature, such as closeness, expression of affection, effective communication, respect, and the nurse-patient bond ²⁸, go in line with our proposal, since we address connection, empathy, inclusion, and confidence, all of which contribute to strengthening the relationship and bonds between nurses and their patients.

The review by the group of experts allowed validating the content of the scale, thus adjusting the degree to which the analyzed items represent the warmth construct and categorizing verbal and non-verbal behaviors with a relevant meaning in the dynamic and fluid communication with the patient, which is crucial to generate a reliable relationship in the care process ²⁹.

After the analysis by experts, the qualitative phase, and the internal structure analysis, we generated the NWS with 35 items reduced into 5 factors, with factorial loads that exceed 0.55 and represent 61% of the total variance ¹⁰.

The NWS reflects warm behaviors associated with the caregiving praxis, which has in turn a humanizing nature when providing nursing care with warmth ³⁰. The presence of warm behaviors in the care provided by nurses not only contributes dynamically to bond formation, but also has positive results in the treatment of patients and can contribute to 85% of the therapeutic effect ³¹.

Factor-1 (Nonverbal-Connection) has items with a high factorial load that mostly describe the absence of warmth, such as Does not smile or looks at the person, but not into the eyes, so that non-verbal communication that favors relational bonds, such as smiling and eye contact ³², is more relevant in their absence, possibly because it is expected. The exchange of messages must contain codes that could be understood and culturally accepted, being the non-verbal component an effective tool to establish contact with patients.

Factor-2 (Empathy) includes items related to the definition of empathy in nursing: "The ability to understand the experiences, concerns and perspectives of another person, added to the ability to communicate this understanding" (33, p. 121). For example, item 13 (It seems that he suffers with me) and item 17 (He gets involved and understands as if he/she were the other person) denote the nurse's ability to perceive and understand the patient from the emotional dimensions of empathy ³³.

The literature confirms that when nursing care goes beyond the biological, empathy becomes a basic need. However, nurses are empathic in contexts that encourage such occurrence, demonstrating that empathy grows with constant reinforcement ³⁴. In this way, the NWS contributes to the identification, understanding and establishment of warm behaviors that represent empathy, thus being able to develop a kind of training that favors the understanding, establishment, and permanence of these care behaviors in health institutions.

Factor-3 (Verbal-Connection) includes items that are related to the importance of verbal communication, including words and voice tone, i.e., item 24 (Speaks in a loud tone, authoritarian), which has a relevant meaning on the message, especially in the conception of the social-voice that incorporates the receiver's interpretation of the acoustic properties of the voice, powerful cues when forming social impressions ³⁵.

For the person receiving care, verbalization reduces tension and anxiety, helps in coping with the experience of the disease, and generates a form of trust, thus verbalizing this feeling will contribute to the healing process. For the nurse, verbalization enables to identify the needs of the sick person ²⁹. Overall, identifying the warm behaviors grouped in this factor contributes to the understanding of the person.

Factor-4 (Inclusion) incorporates behaviors related to induction to the healthcare environment, which implies informing patients about who nurses are and what they do, giving relevance to the first contact that generates a more human therapeutic relationship. In Chile, these aspects are legally regulated, stating that patients have the right to receive understandable information and be treated with kindness ³⁶. The empathic relationship also contributes to the approach and inclusion of the patient within the health area ³¹.

Finally, Factor-5 (Confidence) reasserts the models of warmth and competence impressions ⁸. Confidence is the basis of social practices and is intricately linked to professional competence ⁸.

Knowing warmth-related behaviors associated with trust will allow nurses to show how competent they are in their area without neglecting the warm components of the relationship, strengthening the balance between warmth and competence.

Since warmth influences patient satisfaction ⁶, establishing a level for this construct in order to satisfy the user can be especially useful. Identifying the factors associated with nursing warmth will allow for improved care management, research, and education. However, some cultural aspects must also be considered, since unaccepted behaviors related to personal contact vary among cultures. Therefore, a cross-cultural adaptation is required to be applied in other linguistic contexts ³⁷.

In this study, it was not possible to achieve 10 subjects per variable, as expected ¹⁸. However, an arrangement with high factor loadings was obtained with indices and excellent reliability. To conclude, other methodological contributions should be incorporated in the future, such as the item-response theory.

The NWS is the first scale that measures warmth in the nursing discipline. This tool shows evidence of validity and reliability for the Chilean population and provides the discipline with a new instrument that addresses a relevant dimension for nursing.

Our study provides a scale that incorporates a qualitative phase in its development that involved the contributions of professionals and users for the construction of items, represented in behaviors, which were validated by experts according to the recommendations regarding content validation.