Adult patient:
Clotted blood tube (Serum gel separator clot activator tube)
Minimum blood volume: 5 mL
Paediatric clotted blood tube
Number of vials: 1
Minimum blood volume: 0.8 mL
Authorisation code required
No
24 Hr available service
No
Precaution
Since 17OHP exhibits a diurnal variation similar to that of cortisol, the time of collection should be noted.
Method
Liquid chromatography-tandem mass spectrometry
Reference interval
| Normal neonate (beyond second day) | < 8 |
| Normal child 1 - 6 years | < 3 |
| Normal child 6 - 10 years | < 5 |
| Patient with classical CAH due to CYP 21 defect | > 100 |
| Patient with non-classical CAH | 5 - 200 |
| Heterozygote for classical CAH | < 10 |
| Normal adult males 0800 - 1000 Hr | 1.2 - 5 |
| Normal adult females (follicular phase) | 0.6 - 4.0 |
| Normal adult females (luteal phase) | 1.0 - 6 |
(Source: Clinical Biochemistry, UCLH, Windeyer Building, Cleveland Street, London W1T 4JF based on GC-MS method)
Clinical indication
As part of work-up for females who present with hirsutism or infertility (which may be due to non-classical CAH).
Result interpretation
In patients with normal or mildly elevated basal 17OHP, an ACTH stimulation test may be required to confirm the diagnosis of CAH. (see Short Synacthen Test for CAH).
Low or decreasing 17OHP levels in patients with known CAH indicate a response to treatment. High or increasing 17OHP levels may indicate that adjustment in treatment are required.
Transient elevations in 17OHP level may be observed in preterm infants or infants less than a few days old due to the activation of hypothalamic-pituitary-adrenal axis and the hypothalamic-pituitary-gonadal axis at birth. In preterm infants the elevations can be even more pronounced due to illness and stress.
Measurement of uncertainty
Frequency of measurement
Weekly