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Biomedical subjects

A Langworthy

Publications and source records attributed to A Langworthy.

8 recordsLinked to original sources
PubMed1989

Prognosis in primary biliary cirrhosis: model for decision making.

The ideal mathematical model for predicting survival for individual patients with primary biliary cirrhosis should be based on a small number of inexpensive, noninvasive measurements that are universally available. Such a model would be useful in medical management by aiding in the selection of patients for and timing of orthotopic liver transplantation. This paper describes the development, testing and use of a mathematical model for predicting survival. The Cox regression method and comprehensive data from 312 Mayo Clinic patients with primary biliary cirrhosis were used to derive a model based on patient's age, total serum bilirubin and serum albumin concentrations, prothrombin time and severity of edema. When cross-validated on an independent set of 106 Mayo Clinic primary biliary cirrhosis patients, the model predicted survival accurately. Our model was found to be comparable in quality to two other primary biliary cirrhosis survival models reported in the literature and to have the advantage of not requiring liver biopsy.

Decision Making, Computer-Assisted↗
PubMed1989

Prospective evaluation of esophageal varices in primary biliary cirrhosis: development, natural history, and influence on survival.

The aims of our prospective study were to determine the development and natural history of esophageal varices and variceal bleeding in patients with primary biliary cirrhosis. As part of a controlled clinical study, 265 patients with primary biliary cirrhosis who did not have esophageal varices at entry were followed for a median of 5.6 yr. The mean age was 49 yr (range 26-75 yr), 89% were women, and 69% had advanced histologic stage disease (stage 3-4) on liver biopsy at study entry. All patients were screened annually for esophageal varices by barium esophogram or endoscopy, or both; endoscopy was used to diagnose all episodes of esophageal variceal bleeding. Esophageal varices developed in 83 (31%) patients, and 40 (48%) of those with esophageal varices experienced one or more episodes of esophageal variceal bleeding. Cox regression analysis indicated that only serum bilirubin and histologic stage were associated independently with time to development of esophageal varices. In patients who developed esophageal varices, 33% and 41% developed esophageal variceal bleeding at 1 and 3 yr, respectively. After development of esophageal varices, 1- and 3-yr survival estimates were 83% and 59%, respectively. After the initial variceal bleeding episode, survival estimates were 65% and 46% at 1 and 3 yr and were dependent on Child's classification. These findings are important in considering indications for prophylactic therapy for esophageal varices in primary biliary cirrhosis and may influence timing of liver transplantation.

Adult↗
PubMed1989

Application of the Mayo primary biliary cirrhosis survival model to Mayo liver transplant patients.

Liver transplantation is considered lifesaving for selected patients with end-stage primary biliary cirrhosis (PBC). A mathematical model to predict survival in the patient with PBC who has not undergone transplantation would be valuable for improving selection of patients for and timing of transplantation and for providing control information for assessment of the efficacy of transplantation. The Cox regression method and data from 312 Mayo Clinic patients with PBC were used to develop a model based on age, total serum bilirubin, serum albumin, prothrombin time, and severity of edema. When cross-validated on an independent set of 106 Mayo patients, the model accurately predicted their survival. It was similar to two other published survival models in terms of risk measurement but had the advantage of not necessitating liver biopsy. The model was used to assess the efficacy of liver transplantation by comparing the Kaplan-Meier survival of 32 Mayo patients after transplantation with the average model prediction of survival without transplantation. Beyond 3 months after transplantation, Kaplan-Meier survival probabilities were significantly greater than control survival predicted by the model (P less than 0.001). Examples of using the model for aiding in selection of patients for and timing of transplantation are provided.

Age Factors↗
PubMed1981

Prognosis for central vision and anatomic reattachment in rhegmatogenous retinal detachment with macula detached.

We analyzed a total of 473 eyes with rhegmatogenous retinal detachment and macular involvement for significant factors relating to anatomic success and a favorable visual outcome of 6/15 (20/50) or better. The overall success rate was 90% (427 of 473 eyes). Visual acuities of 6/15 (20/50) or better postoperatively were present in 37% (174 of 470 eyes). Important factors related to both anatomic success and favorable functional results were preoperative visual acuities of 6/15 (20/50) or better, retinal detachments that were less than total, detachments with tears located at or anterior to the equator, absence of giant retinal tears, absence of either preoperative ocular hypotony (tension less than 5 mm Hg) or ocular hypertension (intraocular pressure greater than 20 mm Hg), detachments managed by nondrainage techniques, a single operation with less than 50 cryoapplications, and noncircumferential buckling. Among the other factors related to favorable visual results were detachments lasting less than one month, a shallowly rather than highly detached macula, the absence of fixed retinal folds, a patient age of less than 60 years, and the absence of postoperative choroidal detachments sufficient to cause glaucoma. We found no statistical relationship between either anatomic success or functional result and the presence of aphakia, demarcation lines, vitreous hemorrhage, detachments of the pars plana epithelium, or predetachment glaucoma being treated.

Adolescent↗
PubMed1980

Rhegmatogenous retinal detachment without macular involvement treated with scleral buckling.

Among 173 patients who had rhegmatogenous retinal detachment with spared maculas, high percentage achieved anatomic and functional success. We reattached 171 (99%) of the retinas; 150 (76%) of the eyes had final visual acuities of 6/15 (20/50) or better. Eighteen eyes (10%) had final postoperative visual acuities reduced more than two lines from the preoperative level. This reduced visual acuity was primarily related to postoperative changes occurring in the macula. The prognosis both for anatomic reattachment and visual acuity after scleral buckling for rhegmatogenous retinal detachment is significantly better when the macula is spared than when it is not. Large numbers of cryoapplications were not associated with macular complications.

Adult↗
PubMed1976

An influenza simulation model for immunization studies.

A stochastic simulation epidemic model based on discrete time intervals and appropriate for any infectious agent spread by person-to-person contacts is presented. The population is highly structured, allowing for five age groups and for subgrouping mixing in families, neighborhoods, schools, and preschool playgroups as well as total community mixing. With proper choice of relative susceptibility by age, length of latency and infectivity periods, pathogenicity and withdrawal patterns, and the relative infectiousness of silent infections, the model becomes highly agent-specific. The model includes flexible immunization routines and variable vaccine response patterns. The model is applied to the 1957 Asian and 1968 Hong Kong pandemic strains of influenza A. The results of several schedules of immunization of school children are presented and compared for the two strains.

Adolescent↗