Marga Hoogendoorn

44 nursing staff, this conclusion cannot be made with certainty. Therefore, studies with time- measurements for both the systems and the Nurse:Patient-ratio should be performed before any implications for practice and actions to improve the practice can be made. New time-measurements should also be done for systems still in use but without any update in the last decades, i.e. the TISS, because daily care and treatment may have changed considerably over the years. Finally, another way of assessing the accuracy of the planned staff is comparing the calculated workload with the subjective workload as experienced by nurses. Future studies should focus on how an objectively calculated workload with a workload-system correlates with the subjective workload as experienced by nurses. Implications for practice It is clear that the variety in calculated and overestimation of needed nursing staff could have large consequences for the actual planning of nursing staff. A scoring system should be able to quantify the need for nursing time as accurately as possible to be of any use as a tool for planning nursing staff. The conflicting results and lack of thorough validation make the scoring systems less useful for management decisions. Considering the results of the evaluation of the Nurse:Patient-ratio, the added value of a categorization into a Nurse:Patient-ratio with a system is debatable. If a system is able to measure the actual time needed for nursing care the needed number of nurses can be determinedwithout such a calculated Nurse:Patient-ratio. An accurate calculation of the nursing time needed for certain patient categories should make it possible, on average, to plan the correct number of nurses. It could be that not the Nurse:Patient-ratio, but the workload per patient and therefor per nurse is important for management decisions. This adds to the value of the NAS; with the NAS-points it is possible to calculate the need for nursing time in minutes. The NAS is not calculating an Nurse:Patient-ratio. From a management perspective the balance between needed nursing time according NAS-points and available nursing time in NAS-points is sufficient to measure the workload and calculate the need for nursing staff. Strengths and limitations This study has some strengths and weaknesses. A strength of this study is that we used all relevant literature databases over a long period of time. The titles, abstracts and articles were independently assessed by two different reviewers and inclusion was based on consensus of both reviewers. The included articles cover a period of more than 40 years. It is quite unusual for systematic reviews to include articles over such a long period as the relevance of this literature might become debatable. During a period of 40 years the nursing care on an