Prediction model and web-based risk calculator for postoperative ileus after loop ileostomy closure.

BACKGROUND: Postoperative ileus (POI) is a significant complication after loop ileostomy closure given both its frequency and impact on the patient. The purpose of this study was to develop and externally validate a prediction model for POI after loop ileostomy closure. METHODS: The model was developed and validated according to the TRIPOD checklist for prediction model development and validation. The development cohort included consecutive patients who underwent loop ileostomy closure in two teaching hospitals in Montreal, Canada. Candidate variables considered for inclusion in the model were chosen a priori based on subject knowledge. The final prediction model, which modelled the 30-day cumulative incidence of POI using logistic regression, was selected using the highest area under the receiver operating characteristic curve (AUC) criterion. Model calibration was assessed using the Hosmer-Lemeshow goodness-of-fit test. The model was then validated externally in an independent cohort of similar patients from the University of British Columbia. RESULTS: The development cohort included 531 patients, in whom the incidence of POI was 16·8 per cent. The final model included five variables: age, ASA fitness grade, underlying pathology/treatment, interval between ileostomy creation and closure, and duration of surgery for ileostomy closure (AUC 0·68, 95 per cent c.i. 0·61 to 0·74). The model demonstrated good calibration (P = 0·142). The validation cohort consisted of 216 patients, and the incidence of POI was 15·7 per cent. On external validation, the model maintained good discrimination (AUC 0·72, 0·63 to 0·81) and calibration (P = 0·538). CONCLUSION: A prediction model was developed for POI after loop ileostomy closure and included five variables. The model maintained good performance on external validation.

ANTECEDENTES: El íleo postoperatorio (postoperative ileus, POI) es una complicación importante tras el cierre de la ileostomía en asa, dada su frecuencia e impacto en el paciente. El propósito de este estudio fue desarrollar y validar externamente un modelo de predicción para el POI después del cierre de la ileostomía en asa. MÉTODOS: El modelo fue desarrollado y validado de acuerdo con la lista de verificación TRIPOD para el desarrollo y validación de un modelo de predicción. La cohorte de desarrollo incluyó pacientes consecutivos en los que se realizó el cierre de la ileostomía en asa en dos hospitales universitarios en Montreal, Canadá. Las variables candidatas consideradas para su inclusión en el modelo se seleccionaron a priori en función del conocimiento del problema. El modelo de predicción final, que modeló la incidencia acumulada a 30 días de POI mediante regresión logística, se seleccionó según el criterio del área más alta bajo la curva operativa del receptor (area under the receiver operating curve, AUC). La calibración del modelo se evaluó utilizando la prueba de bondad de ajuste de Hosmer-Lemeshow. El modelo fue posteriormente validado externamente en una cohorte independiente de pacientes similares de la Universidad de British Columbia. RESULTADOS: La cohorte de desarrollo incluyó a 531 pacientes, y la incidencia de POI fue de 16,7%. El modelo final incluyó cinco variables: edad, clasificación ASA (American Society of Anaesthesiologists), patología inicial y tratamiento, tiempo entre las dos intervenciones quirúrgicas y tiempo operatorio del cierre de ileostomía (AUC = 0,68; i.c. del 95%: 0,61 a 0,74). El modelo demostró buena calibración (P = 0,142). La cohorte de validación consistió en 216 pacientes, y la incidencia de POI fue de 15,7%. En la validación externa, el modelo mantuvo una buena discriminación (AUC = 0,72; i.c. del 95%: 0,63 a 0,81) y calibración (P = 0,538). CONCLUSIÓN: Se ha desarrollado un modelo de predicción de POI después del cierre de la ileostomía en asa que incluía cinco variables. El modelo mantuvo un buen funcionamiento en la validación externa.

Development of a direct assay for alpha-amylase.

We describe a direct colorimetric assay for alpha-amylase, with 2-chloro-4-nitrophenyl-alpha-maltotrioside as substrate. Both human pancreatic and salivary amylase split this substrate without the use of helper enzymes, yielding free 2-chloro-4-nitrophenol, which is monitored at 405 nm. The performance of this reagent compares well with that of Pantrak Amylase (Behring Diagnostics) for both serum and urine samples. The reagent is very stable in dry powder form and is stable for one month at 2 to 8 degrees C after reconstitution. Because of the rapid color development and linear kinetics (less than 30 s), the assay is easily automated. Results can be obtained in less than 5 min.

Lecithin:cholesterol acyltransferase activation and lipid binding by synthetic fragments of apolipoprotein C-I.

Peptide fragments of apolipoprotein C-I (apoLP-C-I) have been synthesized by solid phase methodology. After purification, each peptide showed the correct amino acid analysis and was a single band by polyacrylamide gel electrophoresis. In density gradient ultracentrifugation with vesicles of dimyristoyl phosphatidylcholine, peptide fragments 32-57, 24-57, and 17-57 formed stable complexes while 39-57 did not. With mixed vesicles of dimyristoyl phosphatidylcholine-cholesterol 20 micrometer of the fragments 32-57, 24-57 and 17-57 stimulated lecithin:cholesterol acyltransferase (LCAT) activity 50, 60, and 100%, respectively, of the value found for apolipoprotein C-I, while fragment 39-57 was inactive. The results indicate that residues 17-57 contain the structural requirements for LCAT activation by apoLP-C-I, and that residues 32-57 represent one of the major phospholipid-binding regions of apoLP-C-I.

The solid phase synthesis of a protein activator for lecithin-cholesterol acyltransferase corresponding to human plasma apoC-I.

Apolipoprotein C-I, a protein constituent of the very low density lipoproteins of human plasma, consists of a single chain of 57 amino acids. The total synthesis of a protein corresponding to apolipoprotein C-I in physical properties and compositions was accomplished by solid phase techniques employing a modified polystrene incorporating spacer groups between the point of attachment of the first residue and the polymer matrix. The synthetic apoprotein was shown to activate lecithin:cholesterol acyltransferase to the same extent as the native protein. Comparative lipid-binding studies with dimyristoyl phosphatidylcholine gave complexes for native and synthetic apoprotein which floated at the same density after ultracentrifugation in KBr gradients and had virtually the same lipid:protein ratios.