RESUMO
Context: The adrenocorticotropin hormone stimulation test (AST) is used to diagnose adrenal insufficiency, and is often repeated in patients when monitoring recovery of the hypothalamo-pituitary-adrenal axis. Objective: To develop and validate a prediction model that uses previous AST results with new baseline cortisol to predict the result of a new AST. Methods: This was a retrospective, longitudinal cohort study in patients who had undergone at least 2 ASTs, using polynomial regression with backwards variable selection, at a Tertiary UK adult endocrinology center. Model was developed from 258 paired ASTs over 5 years in 175 adults (mean age 52.4 years, SD 16.4), then validated on data from 111 patients over 1 year (51.8, 17.5) from the same center, data collected after model development. Candidate prediction variables included previous test baseline adrenocorticotropin hormone (ACTH), previous test baseline and 30-minute cortisol, days between tests, and new baseline ACTH and cortisol used with calculated cortisol/ACTH ratios to assess 8 candidate predictors. The main outcome measure was a new test cortisol measured 30 minutes after Synacthen administration. Results: Using 258 sequential ASTs from 175 patients for model development and 111 patient tests for model validation, previous baseline cortisol, previous 30-minute cortisol and new baseline cortisol were superior at predicting new 30-minute cortisol (R2 = 0.71 [0.49-0.93], area under the curve [AUC] = 0.97 [0.94-1.0]) than new baseline cortisol alone (R2 = 0.53 [0.22-0.84], AUC = 0.88 [0.81-0.95]). Conclusion: Results of a previous AST can be objectively combined with new early-morning cortisol to predict the results of a new AST better than new early-morning cortisol alone. An online calculator is available at https://endocrinology.shinyapps.io/sheffield_sst_calculator/ for external validation.
RESUMO
An 81-year-old man with a history of ventriculoperitoneal (V-P) shunt placement for symptomatic normal pressure hydrocephalus presented with recurrence of confusion and gait disturbance. Radionuclide cisternography demonstrated loculation of In-111 DTPA in the abdominal wall. A soft tissue mass palpated at the location of tracer accumulation was confirmed to be extraperitoneal pooling of fluid at the site of coiling of the distal shunt tip. After surgical revision, with repositioning of the distal tube in the peritoneal cavity, the patient's symptoms promptly improved. When symptoms of hydrocephalus recur after successful V-P shunt placement, shunt malfunction should be suspected and evaluation for mechanical failure pursued. Catheter migration should be recognized as a correctable cause of shunt malfunction.