Table 1.
Clinical features of two patients with erroneous IPSS results (false negative and false positive)
| Characteristic | False negative (IPSS, ectopic; pathology, CD) | False positive (IPSS, CD; pathology, ectopic) |
|---|---|---|
| Age at diagnosis (yr) | 23 | 54 |
| Sex | Male | Female |
| Symptoms/signs | Weight gain, facial swelling, muscle weakness, violaceous striae, easy bruising, dorsocervical and supraclavicular fat pads | Weight gain, proximal muscle weakness, easy bruising, memory problems, dorsocervical and supraclavicular fat pads |
| ACTH (pg/ml) (normal, <46) | 65.7 | 34.5 |
| 24-h UFC (μg/24 h) (normal, 3.5–45) | 3030 | 27 (eucortisolemic) 755 (hypercortisolemic) |
| CRH stimulation test results suggest | Pituitary | Ectopic (hypercortisolemic) |
| HD DST results suggest | Ectopic | Ectopic (hypercortisolemic) |
| MRI pituitary | 7 mm left pituitary adenoma | Normal |
| IPSS | ||
| Peak ACTH IPS/Pa | 1.3 (347/275) | 9.5 (212/22.4) |
| Baseline PRL IPS/Pa | 1.0 (14.8/15.4) | 1.7 (4.2/2.5) |
| ACTH/PRL IPS/P | 1.3 | 5.6 |
| Surgical pathology | Left 7-mm pituitary adenoma, staining positive for ACTH | Left lower pulmonary carcinoid, staining positive for ACTH |
To convert ACTH level to picomoles per liter, multiply by 0.2202. To convert 24-h UFC level to nanomoles per day, multiply by 2.759. CD, Cushing's disease; HD DST, high-dose dexamethasone suppression test; PRL, prolactin; ectopic, ectopic ACTH secretion.
a
Actual ACTH or prolactin values are shown in parentheses.