Here's why:
* Lack of Theoretical Foundation: Abdellah's 21 nursing problems are not derived from a specific theoretical base. They are a collection of common patient needs and problems identified through clinical experience.
* Limited Scope: The 21 nursing problems lack the breadth and depth of a mid-range theory. They focus on specific patient needs and don't address broader concepts or relationships between concepts.
* Descriptive Nature: Abdellah's work primarily describes and categorizes nursing problems. It does not propose specific relationships or explain phenomena.
Mid-range theories, in contrast, are more abstract and focus on specific phenomena within a larger theoretical framework. They offer explanations, propose relationships, and provide a framework for understanding and guiding nursing practice.
In summary: While Abdellah's 21 nursing problems have been influential in shaping nursing practice, they lack the characteristics of a mid-range theory. They are a valuable framework for identifying patient needs and developing care plans, but they don't offer the level of abstraction and explanation found in a mid-range theory.