Repeatability of the low-dose ACTH test in asthmatic children on inhaled corticosteroids

Recovery of hypothalamo-pituitary-adrenal axis suppression during treatment with inhaled corticosteroids for childhood asthma

Objective

To describe recovery of adrenal insufficiency in asthmatic children treated with inhaled corticosteroids (ICS) and cortisol replacement therapy.

Design

Retrospective, observational study.

Patients

A total of 113 patients, 74 male; age 10.4 (3.3–16.5) years; beclomethasone-equivalent ICS dose, 800 μg, (100–1,000), tested by low dose short Synacthen (tetracosactide) test (LDSST), were studied. Test results were classified by basal and peak cortisol concentration: “normal” (basal >100 nmol/L, peak >500 nmol/L), “suboptimal” (basal >100 nmol/L, peak 350–499 nmol/L), “abnormal” (basal <100 nmol/L and/or peak <350 nmol/L). Patients with suboptimal results received hydrocortisone during periods of stress only, and those with abnormal responses received daily hydrocortisone, increased during periods of stress. A total of 73 patients (68%) had ≥2 LDSSTs over 2.2 years (0.2–7.7).

Measurements

Change in cortisol response to repeat LDSST (movement between diagnostic groups, difference in basal and peak cortisol >15% [2× the inter-assay coefficient of variation]), change in BMI and height standard deviation score (SDS).

Results

Baseline test results were abnormal in 17 patients (15%) and all of them had repeat tests. In 13 patients (76%), test results improved (normal in six, suboptimal in seven) and four (24%) remained abnormal. Baseline tests results were suboptimal in 54 patients (48%), of whom 50 (93%) were retested. Repeat tests were normal in 36 patients (72%), remained suboptimal in 11 (22%), and were abnormal in three (6%). Baseline tests results were normal in 42 patients, of whom six patients (14%) were retested. Results remained normal in three (50%), were suboptimal in two (33%), and abnormal in one (17%). Basal and peak cortisol levels increased by >15% in 33/73 (45%) and 42/73 (57%) patients, respectively, and decreased by >15% in 14/73 (19%) and 7/73 (10%), respectively. There was no significant change in height or BMI SDS.

Conclusion

Recovery of adrenal function is common and occurs during continued ICS and cortisol replacement therapy.

A systematic review and meta-analysis of Synacthen tests for assessing hypothalamic-pituitary-adrenal insufficiency in children

BACKGROUND

The diagnostic value of tests used in assessing hypothalamic-pituitary-adrenal axis (HPA) in children remains controversial.

DESIGN

A systematic review and meta-analysis with receiver-operated-characteristic curve was undertaken to assess the diagnostic values of conventional standard dose 250 μg tetracosactrin (ACTH), short Synacthen test (SSST) and/or low-dose Synacthen test (LDSST) in the assessment of HPA insufficiency in children. Studies eligible for inclusion were any study that compared the use of the LDSST and/or SSST in the assessment of central adrenal insufficiency in children compared with reference standard test.

RESULTS

There were no randomised trials found. SSST resulted in higher specificity and positive likelihood ratio than LDSST. The LDSST had a higher sensitivity (86% vs 61%) but a lower specificity (88% vs 99%) than the SSST, but there was high heterogeneity from the LDSST studies with various doses of Synacthen used.

CONCLUSIONS

Lack of standardisation of assays and protocols with regard to timing, frequency and dose has resulted in diagnostic inaccuracies. There is no clear evidence to indicate that LDSST is superior to SSST in the assessment of HPA axis in children. The choice of either SSST or LDSST should be individualised based on clinical judgement for each patient. This systematic review has identified the need for a well-designed, adequately powered, randomised controlled trial on the use of diagnostic tests used in assessing HPA axis in children.

Adrenal responses to a low-dose short synacthen test in children with asthma

OBJECTIVES

Corticosteroids are known to cause adrenal suppression. The aim of this study was to assess clinical factors affecting responses to a low dose short synacthen test (LDSST) in asthmatic children using corticosteroids.

DESIGN

Patients were recruited from secondary care paediatric asthma populations within the UK.

PATIENTS

Asthmatic children (5-18 years), receiving corticosteroids, underwent a LDSST (n = 525).

MEASUREMENTS

Demographics and corticosteroid doses were tested for association with baseline and peak (stimulated) cortisol concentrations.

RESULTS

Baseline cortisol was significantly associated with age (log baseline increased 0·04 nm per year of age, P < 0·0001), but not with gender or corticosteroid dose. Peak cortisol was significantly associated with total corticosteroid cumulative dose (decreased 0·73 nm per 200 mcg/day, P < 0·001) but not with age, gender inhaled/intranasal corticosteroid cumulative dose or number of courses of rescue corticosteroids. Biochemically impaired response (peak cortisol ≤500 nm) occurred in 37·0% (161/435) overall, including children using GINA low (200-500 mcg/day beclomethasone-CFC equivalent 32%, n = 60), medium (501-1000 mcg/day (33%, n = 57) and high (>1000 mcg/day 40%, n = 13) doses of inhaled corticosteroid (ICS) similarly, and 36·6% of those using fluticasone ICS ≥500 mcg/day (71/194). Impaired response was more frequent in patients on regular oral corticosteroids (66%, n = 27, P < 0·001).

CONCLUSION

Children with asthma can develop biochemical adrenal suppression at similar frequencies for all ICS preparations and doses. The clinical consequence of biochemical suppression needs further study.

Different methods to estimate serum free cortisol: a comparison during cortisol tetracosactide testing

BACKGROUND

Serum cortisol is routinely quantified by immunoassays. In intensive care units serum free cortisol (FC) determination has been described as a better indicator of survival than total cortisol (TC). To estimate FC different methods are available including saliva sampling. We compared five methods to estimate FC, before and after an ACTH stimulating test in patients suspected of adrenal insufficiency.

METHOD

Serum and saliva was collected from 130 patients from the Endocrine Department of a university hospital before and after tetracosactide injection for TC determination. FC was estimated: after serum ultrafiltration, quadratic (Coolens') or cubic (Dorin's) equations, using TC/cortisol-binding globulin concentrations ratio or using cortisol concentration determination in saliva.

RESULTS

FC concentrations obtained by different techniques were significantly correlated and Passing-Bablok regressions showed no deviation from linearity between salFC and filtFC or quadFC. Using the routine assumption that the patients were correctly diagnosed using a post-tetracosactide TC threshold of 550 nmol/L the FC methods generating the best ROC curves were salFC and filtFC or cubFC 30 min after tetracosactide injection.

CONCLUSIONS

FC concentrations obtained by different techniques are significantly but not similarly correlated with TC. As, salFC and filtFC are more convenient to perform than methods involving CBG assays and are better correlated to TC during tetracosactide tests they may be preferred as FC surrogate assays.

Early morning salivary cortisol and cortisone, and adrenal responses to a simplified low-dose short Synacthen test in children with asthma

OBJECTIVE

To examine serum cortisol responses to a simplified low-dose short Synacthen test (LDSST) in children treated with inhaled corticosteroids (ICS) for asthma and to compare these to early morning salivary cortisol (EMSC) and cortisone (EMSCn) levels.

DESIGN

Early morning salivary cortisol and EMSCn samples were collected for three consecutive days. On day three, Synacthen 500 ng/1·73 m(2) was administered intravenously. Samples were collected at 0, 15, 25, 35 min.

RESULTS

A total of 269 subjects (160 M: 109 F), median (range) age 10·0 (5·1-15·2) years were studied. Peak cortisol in the LDSST was <500 nmol/l in 101 subjects (37·5%) and <350 nmol/l in 12 subjects (4·5%). Basal cortisol correlated with peak cortisol: r = 0·55, (95% CI: 0·46, 0·63, P < 0·0001). Time at which peak cortisol concentration was achieved was significantly related to the value of peak cortisol (P < 0·0001), with higher cortisol peaks occurring later in the test and lower cortisol peaks occurring earlier. EMSC and EMSCn had no predictive value for the identification of patients with a peak cortisol <500 nmol/l. EMSCn was superior to EMSC in identifying patients with a peak cortisol <350 nmol/l: a minimum EMSCn cut-off value of 12·5 nmol/l gave a negative predictive value of 99·2% and positive predictive value of 30·1%.

CONCLUSION

Our data illustrate that basal measures of cortisol are likely to be of value in screening populations for patients at greatest risk of adrenal crisis. EMSCn shows promise as a screening tool for the identification of patients with severe adrenal insufficiency.

Lack of sensitivity of the 1-μg low-dose ACTH stimulation test in a paediatric population with suboptimal cortisol responses to insulin-induced hypoglycaemia

CONTEXT

The insulin-tolerance test (ITT) is the gold standard for evaluation of the hypothalamic-pituitary-adrenal (HPA) axis. The low-dose ACTH stimulation test is increasingly used for evaluation of secondary adrenal insufficiency as several studies performed in adults have demonstrated high sensitivity and specificity when compared to the ITT. Whether the ACTH stimulation test demonstrates similar sensitivity in a paediatric and adolescent population compared with the gold standard is unclear.

OBJECTIVE

To compare the sensitivity of the low-dose (1-μg) Synacthen(™) test (LDSST) and the gold-standard ITT in a paediatric and adolescent population.

DESIGN AND PATIENTS

A retrospective review of 42 consecutive LDSSTs in children and adolescents with suboptimal cortisol responses (peak <500 nm) on ITT.

RESULTS

Thirty-one patients (74%) had an adequate cortisol response to low-dose Synacthen(™) (sensitivity 26%). Patients had a higher cortisol increment with the LDSST than ITT (median Δ cortisol 294 vs 168 nm, P < 0.0001) and correspondingly a higher cortisol peak (median peak cortisol 572 vs 396 nm, P < 0.0001). Patients who had a suboptimal peak cortisol both on ITT and on LDSST had a lower baseline cortisol on ITT (median 178 vs 227 nm, P = 0.04). Peak cortisol on ITT was significantly higher in patients who had a subsequent normal LDSST than those that did not (median 417 vs 300 nm, P = 0.0005).

CONCLUSIONS

The 1-μg LDSST lacks sensitivity in detection of secondary adrenal insufficiency in children when compared to the gold-standard ITT.