Nurses constantly make knowledge and skill-based decisions on how to manage patients’ responses to illness and treatment. Their diagnoses should be founded on the ability to analyse and synthesize patients’ information. Accurate formulation of nursing diagnoses is essential, since nursing diagnoses guide intervention [1–4]. It is part of a nurse’ professional role to verify his or her diagnosis with the patient, ‘to be sure that, in the patient’s judgement, the cue cluster represents a problem’ . As stated by the World Alliance for Patient Safety , the lack of standardised nomenclature for reporting hampers good written documentation and may have a negative effect on patient safety internationally . Based on a comparison of four classification systems, Müller-Staub  concluded that the NANDA-I classification is the best-researched and internationally most widely implemented classification system. The definition of ‘nursing diagnosis’ is: “A clinical judgment about individual, family or community responses to actual and potential health problems/life processes. A nursing diagnosis provides the basis for selection of nursing interventions to achieve outcomes for which the nurse is accountable” . An accurate diagnosis describes a patient’s problem (label), related factors (aetiology), and defining characteristics (signs and symptoms) in unequivocal, clear language [1, 3]. Describing a problem solely in terms of its label, in the absence of related factors and defining characteristics, can lead to misinterpretation [1, 5, 10]. Imprecise wording, lack of scrutiny, and expression of patient problems in terms of an incomprehensible diagnosis can have an undesirable effect on the quality of patient care and patient well-being [11, 12]. Nevertheless, several authors have reported that patient records contain relatively few precisely formulated diagnoses, related factors, pertinent signs and symptoms, and poorly documented details of interventions and outcomes [13–15].
Numerous aspects related to cognitive capabilities and knowledge influence diagnostic processes [16, 17]. Knowledge about a patient’s history and about how to interpret relevant patient information is a central factor in deriving accurate diagnoses [18–20]. A distinction between ‘ready knowledge’ and ‘knowledge obtained through the use of knowledge sources’ can be made. Ready knowledge is previously acquired knowledge that an individual can recall. Ready knowledge is achieved through education programmes and experience in situations in different nursing contexts [21, 22]. Knowledge obtained through knowledge sources is acquired through the use of handbooks, protocols, pre-structured data sets, assessment formats, pre-structured record forms, and clinical pathways.
Knowledge sources may help nurses derive diagnoses that are more accurate than those derived without the use of such resources [23, 24]. The purpose of using assessment formats based on Functional Health Patterns and standard nursing diagnoses, as included in the Handbook of Nursing Diagnoses [25, 26], is to attain higher accuracy in diagnoses.
Another factor influencing the accuracy of nursing diagnoses is a nurse’ disposition towards critical thinking and reasoning skills. A disposition towards critical thinking includes open-mindedness, truth-seeking, analyticity, systematicity, inquisitiveness, and maturity . Reasoning skills comprise induction and deduction, as well as analysis, inference, and evaluation. These skills are vital for the diagnostic process [27, 28].
There are two kinds of diagnostic arguments: deductive and inductive. In a deductive argument the premises (foundation, idea, or hypothesis) supply complete evidence for the conclusion so that the conclusion necessarily follows from the premises. In an inductive (diagnostic) argument the premises provide some evidence, but are not completely informative with respect to the truth of the conclusion . It could be noted, identification of a diagnosis is really only one aspect of the clinical reasoning process nurses engage. Clinical reasoning also involves some abduction related to diagnoses as well as interventions and outcomes.
Although, several studies have focused on nurses’ dispositions for critical thinking, these yielded little information about the influence of nurses’ specific reasoning skills in attaining high levels of accuracy of nursing diagnoses [28, 30].