Ineffective Peripheral Tissue Perfusion: Construct Validation Using Rasch Analysis

Sunday, 27 July 2014

R. C. G. Silva, RN, MSc, PhD
Medical-Surgical Nursing Department, Nursing School, University of Sao Paulo, Taboao da Serra, Brazil
Erika de Souza Guedes, MSc, RN
School of Nursing, University of São Paulo, São Paulo, Brazil
Diná de Almeida Lopes Monteiro da Cruz, PhD
School of Nursing, University of Sao Paulo, University of Sao Paulo, Sao Paulo, SP, Brazil

Purpose: The validation of nursing diagnoses is important to nursing practice in clinical, educational and research settings. It allows the refinement of nursing diagnoses classification. Moreover, validation studies allow the identification of diagnostic elements which are able to measure what they are intended to measure, i.e., the diagnosis. There are many methods that can be used to verify the validity of a nursing diagnosis. Fehring’s models are the most frequently used. Among the methods proposed by Fehring the content validation model is the most widely used because it is easier and less expensive. In this context, several nursing diagnoses have been validated. Researchers carried out studies in which Ineffective Peripheral Tissue Perfusion (IPTP) was clinically validated. However, in our best knowledge, there are no studies in which IPTP construct validation by Rasch Analysis was performed. The aim of this study was to verify the IPTP construct validity in patients with intermittent claudication by Rasch Analysis.

Methods: We performed a reanalysis of a previous study database that was carried out by our group and was approved by Ethical Committee. The mentioned study included 65 adult patients with intermittent claudication which did not need assistive devices for ambulation. The reanalysis included data from physical examination, arterial stiffness (carotid-femoral pulse wave velocity – CF-PWV) and functional capacity (six minute walk test). The construct validation was carried out through Rasch Analysis. The concept of construct validity is useful to explain the nature of the nursing diagnosis. In this context, the nursing diagnosis is a defined variable which is placed in a concept system whose relations are explained by a theory. The Rasch analysis is taken as a criterion for the structure of the responses because it considers that the comparison of two people is independent of which items may be used within the set of items assessing the same variable. 

Results: Skin color alteration was the most frequent defining characteristic, i.e., the item with the highest response probability. It measure was -2.54 logito. Skin temperature alteration was the less frequent defining characteristic, i.e., the item with the lowest response probability. It measure was 2.49 logito. CF-PWV and altered walking distance (AWD) response probabilities were 0.05 logito, i.e., very close to the average of items. All defining characteristics (n=14) had appropriate Infit values (between 0.7 and 1.3 logito). It means that they are well adjusted to the model. However, the Outfit values of altered left femoral pulse (FE)  and CF-PWV were 2.33 and 1.63 logito, respectively. In other words, FE and CF-PWV seemed to not properly identify outlier patients. The biserial correlation of FE was -0.2, i.e., it did not belong to the group. Then, we decided to exclude FE of the analysis. It causes an alteration in the adjustment of altered right femoral pulse which, in turn, was excluded of analysis. Twelve items remained in the model. A new Rasch analysis was performed. The remained defining characteristics had good adjustment to the model. The items with the highest and lowest response probabilities were skin color alteration and skin temperature alteration. The probabilities of CF-PWV and AWD were -0.14 logito. Despite this, AWD had better adjustment than CF-PWV. No items had negative correlation or equal to zero. Model reliability was 0.62 and the separation was 1.27.

Conclusion: AWD and CF-PWV seem to contribute to IPTP construct whereas femoral pulses do not.