In this large, multi-center study, we found that the completion of the Pediatric Crohn’s Disease Activity Index and the Abbreviated PCDAI in the context of routine clinical care was quite limited. The components of height velocity, laboratory data, and perirectal examination were the major barriers to completion of these indices. We therefore created a Short PCDAI by eliminating these components, and re-weighting the remaining components to maximize the correlation of the Short PCDAI and the PCDAI. As compared to the full index, this short index is more feasible to complete in the context of routine clinical care and has similar correlation to physician global assessment. The ability to discriminate between inactive and mild disease and between mild and moderate-severe disease is also similar to the full index.
Based on these properties, we believe the Short PCDAI is a promising tool for quality improvement and observational research. It should allow providers to track their patient outcomes over time in a more objective fashion, study how changes in their practices impact patient outcomes, and even allow comparisons to be made to national performance standards (i.e. benchmarking). In addition, this instrument should facilitate retrospective chart reviews and prospective registry studies. Given the myriad of financial and ethical issues, along with the practical issue of difficult recruitment, registries and other observational studies have been a mainstay of clinical research in pediatric IBD for decades. Until now, a significant limitation of such observational studies is the large amount of missing data resulting in possible informational bias when PCDAI was used as an outcome measure, or the inherent subjectivity incurred when Physician Global Assessment was the primary outcome. Hence, the Short PCDAI may optimize the balance between feasibly and objectivity that is necessary for observational research.
Our results regarding the limited ability to complete the PCDAI in the context of routine clinical care are consistent with prior published studies. Turner et al recently published a study indicating that the PCDAI could be completed in less than 50% of visits[12
]. The feasibility of the PCDAI reported in that study was higher than we report, perhaps owing to differences in study design and setting. Turner’s study included patients in the Pediatric IBD Collaborative Research Group, a select group of closely followed newly diagnosed children with IBD. In contrast, rather than a “research study” where careful procedures were used to optimize the completeness of data collected on a limited number of selected patients at selected center, this was a study of actual clinical practice. Participating centers sought to enroll 100% of their patients with Crohn’s disease, and the data in the ImproveCareNow database reflect that captured during routine clinic visits. Therefore, it is not surprising that the completeness of the different clinical indices reported in this study are lower than that reported in other studies. In fact, this underscores the difference between the feasibility of completing an index for a specific research study and the feasibility of completing an index in actual clinical practice.
In our study, we also observed variation in the completeness of PCDAI components across centers. This study included 15 centers, with the largest center contributing approximately 25% of included patients. Therefore, it is possible that this and other large centers might have heavily influenced our results. However, the diversity of sites in the ImproveCareNow collaborative reflect the settings in which pediatric IBD care is delivered in the real world (large and small centers, private and academic practices, etc.)
Our short index differs from the APCDAI in that it does not require the perirectal examination. Prior work has suggested that this component helps discriminate between remission and recurrence with a sensitivity of 32% and a specificity of 98%[15
]. We chose to eliminate this item from our short index because this component of the physical examination is neither indicated nor routinely completed at all outpatient visits. Furthermore, inclusion of this element did not substantially improve the correlation with the full index. Thus, we believe the overall benefit of increased feasibility achieved by eliminating the perirectal exam component is worth this minor trade-off.
It was not possible to select an a. priori threshold for which items to retain in the Short PCDAI. Rather, this threshold was decided after examining the distributions of responses for each component item. If we included completed at less than 80% of visits, the ability to complete the Short PCDAI during routine clinical care would fall to less than two-thirds, greatly limiting the utility of the index. Had we required higher completion rates, this would have eliminated items which are clinically very important and components of most other indices for pediatric and adult IBD (stools, general well-being). Hence, this threshold was selected in order to balance completeness and clinical relevance.
As with the parent PCDAI, the ability of the Short PCDAI to discriminate between inactive and mild disease and between mild and moderate-severe disease is somewhat limited (). This is in part due to the fact that Physician Global Assessment is not a true “gold standard”. Although used as a gold standard in this and other studies evaluating clinical indices in IBD, the subjectivity of this reference limits the ability to actually measure sensitivity and specificity. In a recent evaluation of the PCDAI, the sensitivity and specificity in distinguishing inactive from mild disease was 0.81 and 0.68 respectively, and in distinguishing between mild and moderate-severe was 0.71 and 0.83 respectively[17
]. In the present study, the discriminatory capability of the Short PCDAI was similar, though slightly decreased. This is perhaps due to the fact that PGA was obtained from a large number of practicing clinicians across 15 centers. Although this is a major strength of this study, to the extent that assignment of PGA varies across providers, the sensitivity and specificity of both the full and short index will be diminished. Therefore, the values reported here likely represent a worst-case scenario. In summary, existing pediatric Crohn’s disease activity indices including the PCDAI and APCDAI are of limited value during routine clinical care, as many of the required elements are not always collected and recorded during patient encounters. By retaining and re-weighting the most frequently collected items, we have developed a Short PCDAI that is easier to complete at the point of care, has excellent correlation to the full index, and appears to have a similar ability as the PCDAI to discriminate between different levels of disease activity as measured by Physician Global Assessment. We expect this standardized classification tool will facilitate observational research, quality improvement, and clinical care.