Birgitta Versluijs

75 HRCT after hematopoietic cell transplantation The allo-score, the sum of the HRCT severity score of ground-glass pattern and airtrap- ping, is an easily applicable test with good test characteristics, depending on the cutoff value. To determine the cutoff value for the allo-score, one has to decide whether it is more important to correctly treat early allo-LS with increased immune suppression (ai- ming at high sensitivity and high negative predictive value) or to avoid giving immune suppressive therapy to those who do not need it (aiming at high specificity and high positive predictive value). In our opinion, the optimum should be somewhere between 15 and 25 (Figure 2). Studies addressing the question of diagnostic accuracy of HRCT findings in patients with respiratory problems after hematopoietic cell transplantation are scarce. Most stu- dies look at HRCT signs in patients with a proven specific lung disease and not at the added value of HRCT findings in patients presenting with symptoms. However, the latter strategy is required for diagnostic studies. 19 Our study has several limitations. Although for most HRCT score items the interobser- ver agreement was only moderate, we considered the intraclass coefficient of greater than 0.7 for airtrapping and ground-glass pattern acceptable. In the future, it will be possible to perform computerized calculation of the HRCT score and thus overcome the important issue of reproducibility. Because HRCT results were incorporated in establi- shing the final diagnosis (although the scores were not available), the opportunity for in- corporation bias exists. Nevertheless, given the large difference in HRCT scores between allo-LS and nonallo-LS patients, we believe that bias does not substantially affect our results. The sample size of our study is fairly small, and we propose that our findings be reproduced in an independent cohort. Despite these limitations, we think our findings add to the growing evidence that HRCT is important for diagnosis (and prognosis) in these patients, especially in the early phase after transplantation. In conclusion, our study confirms that the types of HRCT abnormalities considerably overlap between allo-LS and nonallo-LS, but the severity score of certain abnormalities (bronchiectasis, ground-glass pattern, and airtrapping) can differentiate between these complications, especially when applied as the allo-score (ground-glass pattern plus air- trapping). Our findings require confirmation, preferably in an independent prospective cohort, and further testing in more complex diagnostic studies. Early and proper diagno- sis of life-threatening pulmonary complications after hematopoietic cell transplantation is of utmost importance to impact the safety of hematopoietic cell transplantation. 4