Bloodspot 17 alpha-hydroxyprogesterone radioimmunoassay for diagnosis of congenital adrenal hyperplasia and home monitoring of corticosteroid replacement therapy

Therapy monitoring in congenital adrenal hyperplasia by dried blood samples

Careful monitoring of the therapy is crucial for patients with congenital adrenal hyperplasia (CAH) in order to prevent the effects of increased androgen production as well as life-threatening salt-wasting crisis. The key metabolite, 17α-hydroxyprogesterone (17-OHP) can be detected in serum, saliva or dried blood. In clinical practice there are challenges due to discomfort of venous blood sampling and complicated retrieval of saliva during infancy. Furthermore, the immunoassay method is limited in its specificity due to cross-reactions. In this observational study we prospectively examined over a period of 5 years, 20 patients with CAH due to 21-hydroxylase deficiency using standard immunoassays for serum samples (radioimmunoassay and enzyme immunoassay) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) in dried blood spots. Bland-Altman plots show goodness of agreement between both the methods for the desirable therapeutic concentration range of 17-OHP. LC-MS/MS is characterized by a high accuracy in the therapeutic concentration range of 17-OHP <100 nmol/L (r=0.91). Dried blood samples are convenient and reliable specimen for 17-OHP measured by LC-MS/MS. This method could be used for home monitoring of hydrocortisone replacement therapy both in salt-waster and simple virilizer CAH.

Analysis of 17 α-hydroxyprogesterone in bloodspots by liquid chromatography tandem mass spectrometry

Background

Monitoring of treatment for patients diagnosed with congenital adrenal hyperplasia (CAH) can be performed by measuring the concentration of 17α-hydroxyprogesterone (17OHP) in bloodspots collected on filter papers. A method is described here for measuring 17OHP by liquid chromatography tandem mass spectrometry (LCMSMS).

Methods

17OHP was extracted by liquid–liquid extraction and analysed by LCMSMS. The method was validated for sensitivity, specificity, linearity, recovery, ion suppression, precision and bias.

Results

The standard curve was linear from 0 to 400 nmol/L. Intra-assay %CVs were <10 and inter-assay %CVs were <15 over the range 10–200 nmol/L. Limit of quantitation was 6 nmol/L. No ion suppression was detected. The only interfering compound detected was deoxycorticosterone, an intermediate steroid with the same molecular weight as 17α-hydroxyprogesterone. The method was more accurate and precise than an existing radioimmunoassay. There was poor correlation between the two assays.

Conclusions

We have developed a sensitive and specific assay suitable for quantitation of 17OHP in bloodspots. This method performs better than radioimmunoassay and allows smaller samples to be used.

Monitoring of therapy in congenital adrenal hyperplasia

BACKGROUND

Congenital adrenal hyperplasia is a group of disorders caused by defects in the adrenal steroidogenic pathways. In its most common form, 21-hydroxylase deficiency, patients develop varying degrees of glucocorticoid and mineralocorticoid deficiency as well as androgen excess. Therapy is guided by monitoring clinical parameters as well as adrenal hormone and metabolite concentrations.

CONTENT

We review the evidence for clinical and biochemical parameters used in monitoring therapy for congenital adrenal hyperplasia. We discuss the utility of 24-h urine collections for pregnanetriol and 17-ketosteroids as well as serum measurements of 17-hydroxyprogesterone, androstenedione, and testosterone. In addition, we examine the added value of daily hormonal profiles obtained from salivary or blood-spot samples and discuss the limitations of the various assays.

SUMMARY

Clinical parameters such as growth velocity and bone age remain the gold standard for monitoring the adequacy of therapy in congenital adrenal hyperplasia. The use of 24-h urine collections for pregnanetriol and 17-ketosteroid may offer an integrated view of adrenal hormone production but target concentrations must be better defined. Random serum hormone measurements are of little value and fluctuate with time of day and timing relative to glucocorticoid administration. Assays of daily hormonal profiles from saliva or blood spots offer a more detailed assessment of therapeutic control, although salivary assays have variable quality.

A highly specific heterologous enzyme immunoassay for 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide (androstanediol-17G) and developmental patterns of urinary androstanediol-17G excretions

We established a highly specific enzyme immunoassay (EIA) for 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide (androstanediol-17G). Rabbit antisera raised against 5 alpha-androstane-3 alpha, 11 alpha, 17 beta-triol 17-glucuronide 11-glutaryl bovine serum albumin and a heterologous tracer of androstanediol-17G conjugated with horseradish peroxidase at the glucuronic acid group were used. The EIA showed excellent specificity: there were no remarkable cross-reactivities with related androgens. The assay range for urine samples was 0.3-30 ng/ml. Recoveries of standards added to samples were 100-108%. Intra-assay and inter-assay coefficients of variation were 2.9-4.4% and 5.7-7.9%, respectively. The EIA was applied to urine samples of 407 males and 322 females to determine developmental patterns and normal ranges of androstanediol-17G excretions in 11 age groups (0 y, 1 y, 2-3 y, 4-5 y, 6-7 y, 8-9 y, 10-11 y, 12-13 y, 14-15 y, 16-17 y, and over 18 y). Urinary androstanediol-17G/creatinine (androstanediol-17G/Cre) ratios in both sexes were high in infancy, tended to decrease during childhood, and began to increase near adolescence. While androstanediol-17G/Cre ratio in girls increased at 8-9 y and reached a plateau during adolescence, that in boys increased at 10-11 y and continued to increase throughout adolescence. Androstanediol-17G/Cre ratios in girls were higher than those in boys at 6-7 y (P < 0.05) and at 8-9 y (P < 0.01). Androstanediol-17G/Cre ratios in boys were higher than those in girls at 12-13 y and at older ages (P < 0.01). These developmental patterns are parallel to age-related changes in androgenicity and serum androstanediol-17G, suggesting that urinary androstanediol-17G/Cre ratio could be a good marker for androgenicity in childhood.

Early pregnancy diagnosis in swine by direct radioimmunoassay for progesterone in blood spotted on filter paper

A direct radioimmunoassay method for the measurement of progesterone in blood dried on filter paper has been developed for the early pregnancy diagnosis in sows, as well as for monitoring progesterone levels during the oestrous cycle. Pregnancy diagnosis was performed with 95 sows on Days 17-22 after artificial insemination (AI). The cut-off value for pregnancy diagnosis of 7.5 ng/ml was calculated (mean+/-2S.D.) from the progesterone concentrations measured on the same days from non-inseminated animals. There were 85 cases considered pregnant on the basis of progesterone concentration, leaving 10 animals non-pregnant. The accuracy for the positive cases was 98.8%. Two of the 10 sows considered as negative subsequently farrowed, giving an accuracy of 80%. The overall accuracy of the method was 96.8%. The blood-spot assay may be a useful tool for early pregnancy diagnosis in swine, with respect to sampling, simplicity, speed and accuracy.

Correlation of blood-spot 17-hydroxyprogesterone daily profiles and urinary steroid profiles in congenital adrenal hyperplasia

OBJECTIVE

To compare the value of blood-spot 17-hydroxyprogesterone (17-OHP) daily profiles and urinary steroid excretion in untreated and treated patients with congenital adrenal hyperplasia (CAH).

PATIENTS

Ten patients with CAH were investigated during steroid replacement therapy (Group 1), and 11 patients were investigated without treatment (Group 2).

METHODS

Capillary blood samples were collected for measurement of blood-spot 17-OHP values by non-chromatographic radioimmunoassay. Steroid profiles of 24-h urine samples were analyzed by gas chromatography.

RESULTS

There was a close correlation between the individual daily means of blood-spot 17-OHP measurements and the pregnanetriol/ tetrahydrocortisone ratio in both groups of patients (Group 2: r=0.839, p<0.001; Group 1: r=0.686, p<0.001). Almost the same correlation was found between the blood-spot 17-OHP value and the sum of three 17-hydroxyprogesterone metabolites/the sum of three cortisol/cortisone metabolites ratio (Group 2: r=0.918, p<0.001; Group 1: r=0.741, p<0.001).

CONCLUSIONS

Blood-spot 17-OHP measurements and 24-h urinary steroid profile have the same impact in identification and monitoring therapy of children with CAH.

Bloodspot testosterone assay suitable for study of neonates and monitoring of children with congenital adrenal hyperplasia

A bloodspot assay for testosterone has been developed using an antiserum raised against testosterone-3-carboxymethyloxime-bovine serum albumin (T-3 CMO-BSA) conjugate and 125I-T-3CMO-histamine tracer. The method has a detection limit of 0.4 nmol/L with between-batch precision of less than 15% for testosterone values between 0.9 and 2.0 nmol/L and less than 10% for values greater than 2.0 nmol/L. Recovery of 4 nmol/L testosterone spiked into whole blood samples from 16 women (with unspiked bloodspot testosterone concentrations ranging from 0.4 to 3.7 nmol/L) was 100.9%. Bloodspot testosterone concentration was measured in thirty 6-9 day old infants (19 boys, 11 girls) with an absolute range in boys of < 0.4-2.3 nmol/L and in girls of < 0.4 nmol/L. In preterm infants (12 boys, 12 girls) of varying birth gestation and postnatal age, levels were higher than in term infants, with boys showing a rise with increasing postnatal age. Daytime bloodspot profiles in four children on replacement therapy for congenital adrenal hyperplasia demonstrated consistently low testosterone levels in the presence of moderately elevated early morning 17-hydroxyprogesterone concentrations, thus indicating adequate treatment. The bloodspot testosterone assay can be applied to the study of androgen physiology in preterm neonates as well as for monitoring treatment in disorders such as congenital adrenal hyperplasia.

Home monitoring of 17 hydroxyprogesterone levels in congenitx127drenal hyperplasia with filter paper blood samples

OBJECTIVE

The purpose of this study was to evaluate the usefulness of 17 hydroxyprogesterone (17OHP) determination in dried filter paper blood samples from patients with congenital adrenal hyperplasia caused by 21-hydroxylase deficiency. It was hypothesized that these home samples would enhance patient treatment.

STUDY DESIGN

Results of 17OHP determination in simultaneously collected venous and dried filter paper blood samples were compared to establish assay reliability. Thereafter, parents mailed dried filter paper blood samples collected before each hydrocortisone dose.

RESULTS

The 17OHP levels in wet and dried blood samples correlated well (r = 0.98). Results did not change when stored for 2 weeks under various conditions. Blood sampling at different times of the day provided insights into the patterns of 17OHP secretion and identified times of inadequate adrenal suppression. Dose adjustments were then made considering the time of day when adrenal suppression was inadequate.

CONCLUSION

Home monitoring of 17OHP is a reliable and practical approach for assessing adrenal steroid activity in patients with congenital adrenal hyperplasia. Considering the time of day of 17OHP elevations also facilitates hydrocortisone dosing adjustment.

Urinary 17 alpha-hydroxyprogesterone in management of 21-hydroxylase deficiency

OBJECTIVES

The study was designed to assess the reliability of measurement of 24-hour urinary 17 alpha-hydroxyprogesterone (17-OHP) by radio-immunoassay (RIA) as an alternative biochemical assessment for monitoring the treatment of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD) and to assess the need for sample purification by column chromatography to improve assay specificity.

METHODOLOGY

Morning serum 17-OHP was measured using RIA and 24-hour urinary pregnanetriol using gas chromatography. Twenty-four-hour urinary 17-OHP was measured in samples from 17 prepubertal patients with CAH due to 21-OHD, and 20 normal prepubertal children as controls. In 24 urine samples, RIA of 17-OHP was performed with and without column chromatography.

RESULTS

There was a good correlation between 24-hour urinary 17-OHP and 24-hour urinary pregnanetriol (r = 0.962, P < 0.01) and between 24-hour urinary 17-OHP and morning serum 17-OHP (r = 0.955, P < 0.01). There was no significant difference in the RIA of the urine samples with and without purification by column chromatography.

CONCLUSIONS

The measurement of 24-hour urinary 17-OHP is a reliable alternative for the biochemical monitoring of 21-OHD, and RIA specificity is unaffected by omission of column chromatography.

A bloodspot androstenedione assay suitable for home-monitoring of steroid replacement therapy in congenital adrenal hyperplasia

A bloodspot assay has been developed using an antiserum raised against androstenedione-3-carboxymethyloxime-bovine serum albumin (AD-3CMO-BSA) conjugate and 125I-AD-3CMO-histamine tracer. The method has a detection limit of 0.6 nmol/L blood and a working range from 0.6 to 40 nmol/L blood. The between-batch precision ranged from 8.4% to 23.3%. Bloodspot androstenedione (AD) concentrations were measured in 50 neonates (26 male, 24 female) and in 95 children (54 male, 41 female) aged 6 months to 18 years. No sex difference in concentrations was found in neonates, in pre-pubertal children up to 8 years of age, in pubertal children (males 8-16 years, females 8-14 years) or post-puberty. Bloodspot AD concentrations ranged from less than 0.6 to 2.7 nmol/L in neonates, less than 0.6 nmol/L in pre-pubertal children, 0.6-2.1 nmol/L in pubertal children and less than 0.6-4.6 nmol/L post-puberty. Daytime bloodspot profiles in 10 children on replacement therapy for congenital adrenal hyperplasia generally showed good correlation between 17 alpha-hydroxyprogesterone and AD concentrations (r = 0.928, P less than 0.001). Bloodspot AD profiles have advantages over 17 alpha-hydroxyprogesterone profiles for the assessment of the adequacy of glucocorticoid replacement therapy.

Blood spot glucocorticoid concentrations in ill preterm infants

The adrenocortical response to stress was studied longitudinally in 10 ill preterm infants using measurements of cortisol and 170H-progesterone concentrations in filter paper blood spots. Mean cortisol and 170H-progesterone concentrations reached a peak of 2200 nmol/l and 65 nmol/l, respectively, between the third and fifth days of life. These concentrations far exceeded those observed in older children and adults subjected to stress as a result of surgery. Further pulses of endogenous cortisol production of 4000 nmol/l or more occurred in association with clinical complications such as intraventricular haemorrhage. These results indicate that infants undergoing intensive care are unduly stressed. Consideration should be given to providing enough sedation and appropriate analgesia for ill preterm infants during painful procedures such as insertion of venous cannulae and arterial puncture.

Radioimmunoassay of blood-spot 17 alpha-hydroxyprogesterone in the management of congenital adrenal hyperplasia

A robust assay for routine measurement of blood-spot 17 alpha-hydroxyprogesterone (17-OHP) concentrations has been developed using a magnetizable, solid-phase antiserum and an 125I-radioligand. The working range of this assay (13.5-500 nmol/L) is well suited for the initial diagnosis of congenital adrenal hyperplasia (CAH) and for monitoring replacement therapy in CAH patients. Data derived from multiple blood-spot samples, collected on two consecutive days, provide 17-OHP profiles. These profiles have been used to construct a chart allowing a rapid visual assessment of the efficacy of replacement therapy in CAH patients. Measurement of 17-OHP in the blood-spots of overtreated patients and accurate determination of normal range values in healthy infants relied on development of a sensitive assay (range 1.7-34 nmol/L). In the blood-spots of normal male (n = 50) and female (n = 50) infants collected 5-7 days after birth, 17-OHP concentrations were 7.62 +/- 2.55 nmol/L and 7.32 +/- 2.87 nmol/L respectively. Retrospective measurement of this steroid in samples from known CAH patients (n = 4), which had values ranging from 224 to 2145 nmol/L, support a role for measurement of blood-spot 17-OHP in high-risk screening programmes.

The interpretation of bloodspot 17 alpha-hydroxyprogesterone levels in term and pre-term neonates

Bloodspot 17 alpha-hydroxyprogesterone, plasma cortisol, plasma sodium and urinary 17 alpha-hydroxyprogesterone, cortisol, sodium and creatinine levels were determined in 24 term and 32 pre-term infants on the third, eighth and fourteenth days of life. Pre-term infants, whether 'well' or 'sick', had significantly raised bloodspot 17 alpha-hydroxyprogesterone levels (up to 158 nmol/L) compared with those found in term infants (up to 18.8 nmol/L). Urinary 17 alpha-hydroxyprogesterone creatinine ratios were also higher in pre-term infants. Plasma cortisol results showed similar ranges for term and pre-term infants, and bloodspot 17 alpha-hydroxyprogesterone/plasma cortisol ratios for day 3 specimens correlated with the degree of prematurity. These results may be due either to immature enzyme systems in the pre-term baby or to an excess of related steroids cross-reacting in the 17 alpha-hydroxyprogesterone assay. We propose the use of two distinct upper limits of normal of 20 nmol/L (term infants) and 200 nmol/L (pre-term infants), for the interpretation of bloodspot 17 alpha-hydroxyprogesterone levels at the end of the first week of life.

Response to ACTH in the newborn

Adrenocortical function was studied in 52 newborn infants who had been divided into three groups: preterm well, preterm ill, and term ill. Basal plasma 17-hydroxyprogesterone concentrations were significantly increased in both groups of preterm infants. There was no significant difference in basal plasma cortisol concentrations, although they were highest in preterm ill infants. All infants responded to adrenocorticotrophic hormone (ACTH) stimulation (36 micrograms/kg intramuscularly) with a two to three fold increase in the concentration of both steroids. The peak plasma 17-hydroxyprogesterone response was significantly higher in preterm ill infants. A subgroup of five infants, who were highly stressed but had undetectable basal plasma cortisol concentrations, also showed an appropriate response to ACTH. The results provide useful reference data to assess adrenal function in the infant of a mother given glucocorticoids during pregnancy. There is also a change from the pattern of fetal adrenal steroidogenesis soon after birth, which may be affected by exogenous ACTH stimulation. Roughly 10% of stressed newborns failed to synthesise cortisol basally; temporary glucocorticoid replacement for such infants may be appropriate.

Patient-orientated metered capillary blood collection

A small collector bottle, with a precision-moulded top, allows capillary blood from a finger-prick to be automatically metered into a diluent for subsequent laboratory analysis. This device, which has been successfully used by patients to obtain full blood counts, glycosylated haemoglobin values and blood glucose measurements, may have wide application.