Factors associated with hospital readmission in sickle cell disease

The study sample comprised all patients admitted, from 2000 to 2004, to a university hospital in Rio de Janeiro State, south-east Brazil, as a result of acute complications from sickle cell disease (SCD). Considering the statistical problem of studying individuals with multiple events over time, the following extensions of Cox's proportional hazard ratio model were compared: the independent increment marginal model (Andersen-Gill) and the random effects model.The study considered 71 patients, who were admitted 223 times for acute events related to SCD. The hazard ratios for hospital readmission were statistically significant for the prior occurrence of vaso-occlusive crisis and development of renal failure. However, analysis of residuals of the marginal model revealed evidence of non-proportionality for some covariates.the results from applying the two models were generally similar, indicating that the findings are not highly sensitive to different approaches. The better fit by the frailty model suggests that there are unmeasured individual factors with impact on hospital readmission.In Brazil, sickle cell disease (SCD) is the most prevalent of the hereditary diseases, particularly among Afro-descendants. It is characterised by mutation of the beta globin chain gene, producing an abnormal variant called haemoglobin S (HbS) [1]. Abnormal haemoglobin can cause various clinical events, the most common being vaso-occlusive crisis (VOC), characterised by acute episodes of abdominal, thoracic and bone pain and chronic haemolytic anaemia. These events, particularly VOC, require hospital care [2,3].The disease evolves very differently from patient to patient and this variability seems to be related to hereditary and environmental factors, including aspects of socio-economic situation. While the disease progresses benignly and even without symptoms in some patients, others are more prone to complications, and a small subgroup has high rates of VOC and requires multiple hospi