An association between quality of care and staffing levels, particularly registered nurses, has been established in acute hospitals. Recently an association between nurse staffing and quality of care for several chronic conditions has also been demonstrated for primary care in English general practice. A smaller body of literature identifies organisational factors, in particular issues of human resource management, as being a dominant factor. However the literature has tended to consider staffing and organisational factors separately.

We aim to determine whether relationships between the quality of clinical care and nurse staffing in general practice are attenuated or enhanced when organisational factors associated with quality of care are considered. We further aim to determine the relative contribution and interaction between these factors.

We used routinely collected data from 8409 English general practices. The data, on organisational factors and the quality of clinical care for a range of long term conditions, is gathered as part of “Quality and Outcomes Framework” pay for performance system. Regression models exploring the relationship of staffing and organisational factors with care quality were fitted using MPLUS statistical modelling software.

Higher levels of nurse staffing, clinical recording, education and reflection on the results of patient surveys were significantly associated with improved clinical care for COPD, CHD, Diabetes and Hypothyroidism after controlling for organisational factors. There was some evidence of attenuation of the estimated nurse staffing effect when organisational factors were considered, but this was small. The effect of staffing interacted significantly with the effect of organisational factors. Overall however, the characteristics that emerged as the strongest predictors of quality of clinical care were not staffing levels but the organisational factors of clinical recording, education and training and use of patient experience surveys.

Organisational factors contribute significantly to observed variation in the quality of care in English general practices. Levels of nurse staffing have an independent association with quality but also interact with organisational factors. The observed relationships are not necessarily causal but a causal relationship is plausible. The benefits and importance of education, training and personal development of nursing and other practice staff was clearly indicated.