Marga Hoogendoorn

42 agreement. Because the duration of the activity has to be estimated, the assessment is partly subjective. This subjective estimation can lead to differences in NAS-scores and subsequently to differences in the calculated need for nursing staff. We indicated the use of time-measurements or Multi Moment Recordings as the gold- standard for the development and validation of a system to quantify nursing time needed. This method was, however, only used in six of the 27 (22%) scoring systems. For all those systems the results showed a good validity. The most common method used for validation of a new system was the comparison with an already existing system. TISS was most frequently used for this purpose. Although the TISS-76 was developed without time measurements, a later version of TISS-76 was in fact validated with the gold standard (i.e. time-measurements), but not before 1992 15, 46 . Despite the lack of formal validation, the TISS-76 was already used as a reference in validation studies of other systems before 1992. Overall, the NAS performed best as it was developed by nurses, validated with time- measurements and explaining 80% of the nursing activities. The reliability varied between low to good. The studies which reported low reliability explicitly evaluated the reliability of scoring systems with categories of estimated time per intervention. This can be explained by the psychometric properties of these questions. The answers on subjective questions are more influenced by external factors as the involved observer self and knowledge of the definitions of those questions. Education and training in the use of the NAS is therefore necessary for a better use of this system. Furthermore, as more and more Intensive Cares are equipped with electronic patient records or patient data management systems, automatic bedside registration in an electronic patient record could also lead to more unambiguous scoring and improved reliability of the NAS. Translation of a scoring system into another language is also known to influence the reliability 86 . This is important for the NAS, because the NAS is widely used, among others, in countries with Portuguese language. We found one study reporting about the psychometric properties of a translated Portuguese version of the NAS. This study concluded that the Portuguese version of the NAS was found to be a valid instrument 74 . One study in 7 different countries in Europe and Brazil showed a large variation in NAS scores, ranging from a mean NAS per patient of 101.8 in a Norwegian Intensive Care to 44.5 in a Spanish Intensive Care 87 . We recognize this variation also in other studies included in our review. This could partly be explained by the fact that the studies are conducted in different countries with different organization structures of the Intensive