Background
Kawasaki disease (KD) is an acute febrile illness characterized by multisystemic vasculitis, which usually may be associated with coronary artery lesions (CALs), and has been considered as the most common cause of acquired heart disease among children in industrialized countries. Although the treatment of intravenous immunoglobulin (IVIG) plus aspirin has greatly decreased the incidence of CALs within the first 10 days of fever onset, previous studies indicated that 10-20% of patients with KD were unresponsive to initial treatment with IVIG, and even 20-30% of patients resistant to initial treatment with IVIG did not respond to a second dose of IVIG [1, 2]. This condition could be more prone to risk of CALs.
Increasing evidence has confirmed that systemic inflammation and immune responses play a crucial role in the pathogenesis and progression of KD. Several prognostic models for IVIG resistant KD have been widely investigated, such as the Formosa scoring system from Taiwan, China, the San Diego scoring system from American, and the Kobayashi, Egami and Sano scoring system from Japan. However, these models have been relatively lacking in the Mainland of China [3]. A large number of studies also attempted to search markers for predicting IVIG resistant KD. Recently, it was reported that the peripheral biomarker of immunity/inflammation, the neutrophil-to-lymphocyte ratio (NLR), and platelet (PLT)-to-lymphocyte ratio (PLR) were identified as significant prognostic indicators in KD with IVIG resistance [4-6]. In addition, serum albumin, known as an indicator of host inflammatory and nutritional status, had been confirmed to have a prognostic role in the Chinese population with IVIG resistant KD [7]. However, these models or indicators were not satisfactory for predicting IVIG resistance in clinical practice. Recently, it has been hypothesized that immunonutritional status could reflect the general condition of patients, including immunocompetence, protein turnover and physical condition. The prognostic nutritional index (PNI) based on a combination of albumin levels and peripheral blood lymphocyte count, was supposed to show a more accurate representation of the nutritional and immunological status in various types of cancer [8]. Its prognostic value in various types of tumor, such as urinary cancer, tongue squamous cell carcinoma [9], osteosarcoma [10], gynecological cancer [11], non-small cell lung cancer[12] and pulmonary embolism[13], acute myocardial infarction[14, 15], idiopathic dilated cardiomyopathy [16] and heart failure [17] has been widely investigated. Recently, Tai et al reported that a low pre-treatment PNI level (PNI<55) correlated to a high incidence of CALs, as well as IVIG non-responder in 275 children with KD from Taiwan [18], but the sample size was small and cases were came from only one institution. Therefore, the present study was designed in order to further determine whether PNI could predict IVIG resistance in large cohort of patients with KD from six institutions.