Measurement of 25-hydroxyvitamin D in the clinical laboratory: current procedures, performance characteristics and limitations

In this review we describe procedures, performance characteristics and limitations of methods available for the measurement of 25-hydroxyvitamin (25OHD) since the year 2000. The two main types of methods are competitive immunoassay and those based on chromatographic separation followed by non-immunological direct detection (HPLC, LC-MS/MS). Lack of a reference standard for 25OHD has, until recently, been a major issue resulting in poor between-method comparability. Fortunately this should soon improve due to the recent introduction of a standard reference material in human serum (SRM 972) from the National Institute of Standards and Technology (NIST). For immunoassay, specificity can be an issue especially in relation to the proportion of 25OHD2 that is quantified whereas HPLC and LC-MS/MS methods are able to measure the two major vitamin D metabolites 25OHD2 and 25OHD3 independently. HPLC and LC-MS/MS require more expensive equipment and expert staff but this can be offset against lower reagent costs. Increasingly procedures are being developed to semi-automate or automate HPLC and LC-MS/MS but run times remain considerably longer than for immunoassays especially if performed on automated platforms. For most HPLC and LC-MS/MS methods extraction and procedural losses are corrected for by the inclusion of an internal standard which, in part, may account for higher results compared to immunoassay. In general precision of immunoassay, HPLC and LC-MS/MS are comparable and all have the required sensitivity to identify severe vitamin D deficiency. Looking to the future it is hoped that the imminent introduction of a standard reference method (or methods) for 25OHD will further accelerate improvements in between method comparability.

The concordance between serum anti-Mullerian hormone and testosterone concentrations depends on duration of hCG stimulation in boys undergoing investigation of gonadal function

BACKGROUND

In boys undergoing investigation of gonadal function, the relationship between a single measurement of serum anti-Mullerian hormone (AMH) and hCG stimulated serum testosterone is unclear.

AIM

The aim of the study was to assess concordance between serum AMH and testosterone concentrations following hCG stimulation of two different durations.

METHODS

Samples from 284 children (M : F, 154 : 130) with a median age of 8 years (10th, 90th centiles, 0.25, 14) were used to establish an AMH reference range. Clinical data were reviewed in boys undergoing investigation of gonadal function and who had an AMH measurement and a hCG stimulated (3-day or 3-week) (n = 26) testosterone. Of these 26 boys, 11 had combined genital anomalies, whereas the rest had conditions such as isolated hypospadias, undescended testes or microphallus. Normal testosterone response to hCG stimulation was defined as a level greater than 3.5 nmol at day 4 and 9.5 nmol/l at day 22.

RESULTS

In the reference group, the 5th centile AMH for boys below 1 year was 215 pmol/l and between 1 and 8 years 180 pmol/l. The 95th centile for girls for these respective age groups was 30 pmol/l and 25 pmol/l. In those cases where serum testosterone concentrations were available at day 1, day 4 and day 22 of the 3 week-hCG test, five cases had a normal serum testosterone at day 4 and three cases only showed such a response by day 22. In those where serum AMH was less than 180 pmol/l, a poor testosterone response of less than 3.5 nmol was observed in approximately seven of eight (88%) cases with a 3-day hCG stimulation test or the 3-week test. An AMH of greater than 180 pmol/l was associated with a normal testosterone response at day 4 in 10 out of 15 (67%) cases and at day 22 in eight of 11 (73%) cases. However, a low serum testosterone concentration of less than 3.5 nmol after the 3-day hCG test was only associated with a likelihood of a low AMH in three of eight (37%) cases. With the 3-week hCG test, a low day 22 testosterone of 9.5 mmol/l or less was associated with a low AMH of 180 pmol/l or less in four of seven (57%) cases.

CONCLUSION

In boys undergoing investigation of gonadal function, the concordance between AMH and testosterone is better at day 22 than day 4. A normal AMH may provide useful information on overall testicular function but does not exclude the need for an hCG stimulation test.

A screening procedure for primary aldosteronism based on the Diasorin Liaison® automated chemiluminescent immunoassay for direct renin

Background

Primary aldosteronism (PA), the most common secondary cause of hypertension, can be screened for using the aldosterone/renin ratio. This ratio is raised in PA and its accuracy depends on the ability to measure plasma renin at extremely low concentrations.

Methods

We compared two different procedures for assessing plasma renin. The conventional method, which measures plasma renin activity (PRA), is technically demanding and laborious, and the Diasorin Liaison® method, which measures plasma renin concentration (PRC), is an automated immunoassay. Results from each method were used to calculate the aldosterone/renin ratio (ARR) and the performance of the Diasorin Liaison® method compared with that of the conventional assay using receiver operator characteristic curves.

Results

The analytical and functional sensitivity of the PRC method were 2.1 and 5 μIU/mL, respectively. Intra- and inter-assay precision were <7.2% and 10.4%, respectively. There was significant (9%) prorenin interference. Samples with PRA > 1.0 ng/mL/h showed significant correlation with PRC ( r = 0.93; P < 0.05; n = 146); however, with PRA < 1.0 ng/mL/h, no significant correlation occurred ( r = 0.14; P < 0.05; n = 79). An aldosterone (pmol/L)/PRC(μIU/mL) ratio of >35, in patients with aldosterone >300 pmol/L, resulted in 100% sensitivity and 93% specificity, when compared with the commonly accepted aldosterone (pmol/L)/PRA (ng/mL/h) ratio of >750, in identifying patients who may suffer from PA.

Conclusion

This study indicates the feasibility of using the automated PRC assay as a replacement for the conventional manual PRA assay in calculating the ARR as a first-line screen for PA.

Exaggerated adrenarche in a cohort of Scottish children: clinical features and biochemistry

OBJECTIVE

To investigate the reported association between exaggerated adrenarche (EA) and reduced foetal growth and to identify possible risk factors for future morbidity in Scottish children with clinical features of EA.

DESIGN

Three-year prospective study.

MEASUREMENTS

Auxology, blood pressure (BP), biochemical analysis of blood and urine, pelvic ultrasound in girls.

RESULTS

Fifty-two patients were recruited of whom one girl had nonclassical congenital adrenal hyperplasia (17-OHP 17 nmol/l) and one had insufficient blood for analysis. The final cohort comprised 42 girls of mean (SD) age 7.7 (0.99) and eight boys of 8.8 (0.67) years. Mean (SD) birth weight was 3.27 (0.49) and 3.10 (0.76) kg in girls and boys respectively. Height/weight SDS were 1.13/1.69 in girls and 1.69/1.88 in boys. Mean systolic/diastolic BP was 107.8/60.4 (50th-75th centile) in girls and 115.5/63.9 (75th-91st centile) in boys. Uterine and ovarian development was prepubertal. Median serum dehydroepiandrosterone sulphate (DHEAS) was 2.1 and 4.1 mumol/l, androstenedione 3.1 and 3.8 nmol/l in girls and boys respectively, with DHEAS within the reference range/undetectable in 18/2 and androstenedione in 12/6 patients. Fasting insulin was 9.0 and 15.0 mU/l in girls and boys respectively, with concomitant low normal SHBG. Anti-Mullerian hormone (AMH) was 15.7 pmol/l in 27 girls, compared with 5.0 pmol/l in normal girls aged 5-8 years.

CONCLUSIONS

Our Scottish EA cohort showed female predominance, no evidence of reduced foetal growth, a tendency to overweight with commensurate mild hyperinsulinaemia and modest elevation of serum androgens in some patients. We have found raised AMH levels in the girls, indicating advanced ovarian follicular development.

Sentinel lymph node accumulation of Lymphoseek and Tc-99m-sulfur colloid using a "2-day" protocol

Lymphoseek is a receptor-binding radiopharmaceutical specifically designed for sentinel lymph node (SLN) mapping. We conducted a clinical trial which measured the injection site clearance and sentinel lymph node accumulation after a single intradermal injection of Lymphoseek or unfiltered [(99m)Tc]sulfur colloid (TcSC) using a "2-day" protocol for SLN mapping of breast cancer. Eleven patients with breast cancer participated in this study. Five patients received an intradermal administration of 1.0 nmol of (99m)Tc-labeled Lymphoseek; SLN mapping was performed on four subjects within 19 to 27 h. Six subjects received an intradermal administration of TcSC; SLN mapping was performed on five subjects within 18 to 26 h. Lymphoseek exhibited a significantly (P<.001) faster injection site clearance than TcSC. The mean Lymphoseek clearance half-time was 2.18+/-1.09 h compared to 57.4+/-92.8 h for TcSC. The mean sentinel lymph node uptake of Lymphoseek (1.5+/-1.7%) and TcSC (3.5+/-3.1%) was statistically equivalent (P=.213). When an intradermal injection is employed, Lymphoseek demonstrated faster injection site clearance than unfiltered [(99m)Tc]sulfur colloid and persistent SLN accumulation for at least 24 h.

Short‐term growth and bone turnover in children undergoing occlusive steroid (‘Wet‐Wrap’) dressings for treatment of atopic eczema

To assess the effects of steroid wet-wrap therapy on short-term growth and bone turnover, eight prepubertal (M:F,5:3) children with a median age of 5.1years (range 3.3-8.8) were studied over a 2-week period prior to therapy and at 2-week intervals during therapy. Short-term growth was assessed by measuring lower leg length velocity (LLLV) by knemometry and bone and collagen turnover was assessed by urinary deoxypyridinoline crosslink excretion corrected for creatinine excretion (DPD). Median duration of study during occlusive dressings was 12 weeks (range 2-18). Topical beclomethasone dipropionate diluted 1:10 or 1:4 in white soft paraffin was applied under tubular (Tubifast) bandages in 7/8 children. Median LLLV before and during therapy were 0.43 mm/week (10(th),90(th) centile; 0.0,0.7) and 0.42 mm/week (10(th),90(th) centile; -0.35,1.01), respectively (not significant). Median DPD before and during therapy were 25.9 nmol/l/creatinine (10(th),90(th) centile; 20.8, 33.0) and 26.3 nmol/l/creatinine (10(th),90(th) centile; 21.7, 34.1) respectively (not significant). Non-invasive assessment of the effects of steroid wet-wrap therapy can be performed in children with eczema. These preliminary results show no substantial growth promoting or adverse effects of therapy.

A 5-year-old boy with cryptorchidism and pubic hair: investigation and management of apparent male disorders of sex development in mid-childhood

BACKGROUND

Late presentation of congenital adrenal hyperplasia as a 46,XX disorder of sex development due to 11-beta hydroxylase deficiency is uncommon. Such a case raises issues regarding appropriate investigation and management.

CASE HISTORY

A 5-year-old boy who had recently moved to the United Kingdom presented at the endocrinology clinic with recurrent abdominal pain. He was normotensive and had a history of ambiguous genitalia since birth, a relatively small penis, bilateral cryptorchidism and pubic hair. A systematic workup revealed low anti-Mullerian hormone levels for age and sex and elevated serum testosterone, androstenedione and deoxycortisol levels. A urinary steroid profile confirmed a diagnosis of 11-beta hydroxylase deficiency. The child's karyotype was 46,XX. Further genetic analysis revealed a compound heterozygote mutation in the CYP11B1 gene. Ultrasound scan showed evidence of Mullerian structures and accumulation of menstrual blood in the vagina (haematocolpos). Following discussion at a multidisciplinary clinic, the patient did not undergo sex reassignment and subsequently proceeded to surgery for removal of the Mullerian structures.

CONCLUSIONS

This case emphasizes the importance of a systematic approach to investigation of older children presenting with apparent male undermasculinisation. It also raises important issues about gender reassignment in mid-childhood and the indications for removal of Mullerian organs in a 46,XX boy.

Feline combined diaphyseal radial and ulnar fractures. A retrospective study of 28 cases

Feline combined diaphyseal radial and ulnar fractures were reviewed in a retrospective study of cases that were admitted to two university teaching hospitals. A high incidence of complications was noted, with 6/26 (23.1%) of cases requiring revision surgery. Open fractures were significantly more likely to require revision surgery. The two main repair methods were external skeletal fixation (ESF) or radial plating. The success rate was greater for radial plating, with only 1/10 (10%) cases requiring revision versus 4/14 (28.6%) for ESF. However, ESF tended to be applied to the more complicated fractures. Stabilisation of both bones proved to be an effective repair strategy with only 1/8 cases (12.5%) requiring revision versus 5/18 cases (27.8%) where only one bone was stabilised. Synostoses and radiohumeral luxation were noted as complications associated with the fractures stabilised by ESF. Final limb function following recovery was assessed as 'good' or 'excellent' in 93.3% of cases.

Effect of moderate-intensity exercise session on preprandial and postprandial responses of circulating ghrelin and appetite

Responses of plasma total ghrelin and appetite were investigated during preprandial and postprandial stages of recovery from a moderate-intensity cycling session. Healthy recreationally active men underwent one exercise and one control trial. In the exercise trial, subjects exercised for approximately 60 minutes, while in the control trial they rested quietly for the same duration. After the intervention, subjects rested for 120 minutes and then consumed a test meal. Measurements were obtained immediately and 120 minutes after the intervention and then during 180 minutes of the postprandial period. The post-intervention concentration of total ghrelin was lower (p<0.05) in the exercise than in the control trial. The modulating effect of exercise was related to the reduction in the postprandial rather than preprandial concentration. Post-intervention scores of appetite were not different between the two trials, but when preprandial and postprandial responses were considered separately, postprandial hunger and desire to eat was higher (p<0.05) in the exercise trial. In summary, during recovery from moderate-intensity exercise, total ghrelin does not respond in a compensatory manner to disturbances in energy balance. Thus, an exercise-induced increase in appetite during the later stages of recovery coinciding with the postprandial state cannot be explained by changes in the plasma concentration of total ghrelin.

Effect of variation in CYP11B1 and CYP11B2 on corticosteroid phenotype and hypothalamic-pituitary-adrenal axis activity in hypertensive and normotensive subjects

BACKGROUND

Aldosterone is important in the development of hypertension. We have shown that a single nucleotide polymorphism (SNP) (-344T) in the 5' regulatory region (UTR) of the gene encoding aldosterone synthase (CYP11B2) associates with aldosterone excess and hypertension as well as altered adrenal 11-hydroxylation efficiency (deoxycortisol to cortisol). This conversion is carried out by the enzyme 11beta-hydroxylase, encoded by the adjacent gene, CYP11B1. We proposed that the effects of CYP11B2 are explained by linkage disequilibrium (LD) across the CYP11B locus. We have demonstrated high LD across this locus and identified two SNPs in the 5' UTR of CYP11B1 (-1859 G/T, -1889 A/G) that associate with reduced transcription in vitro and altered 11-hydroxylation efficiency in vivo. Accordingly, we hypothesized that the reduced adrenal 11-hydroxylation may lead to chronic resetting of the pituitary-adrenal axis, with chronically increased ACTH drive resulting in aldosterone excess.

METHODS

To test this, we examined hypothalamic-pituitary-adrenal (HPA) axis activity in hypertensive and normotensive individuals stratified according to genotype at CYP11B2 (-344T/C) and CYP11B1 (-1859 G/T, -1889 A/G). Fifty-six subjects homozygous for CYP11B2 SNP (27 TT, 12 CC), and 38 homozygous for CYP11B1 SNPs (18 TTGG, 20 GGAA) were recruited. Diurnal variation and the effects of dexamethasone suppression and ACTH stimulation on plasma aldosterone, cortisol and ACTH under controlled conditions were studied.

RESULTS

Subjects with SNPs associated with reduced 11-hydroxylation efficiency (-344T CYP11B2; TTGG CYP11B1) showed reduced inhibition of ACTH after dexamethasone (P = 0.05) and an altered cortisol-ACTH relationship (decreased cortisol-ACTH ratio, P < 0.02). The same individuals also demonstrated close correlations between plasma cortisol and aldosterone (-344T CYP11B2 r = 0.508, P < 0.004; TTGG CYP11B1 r = 0.563, P < 0.003) suggesting that there was common regulation (possibly ACTH) of these hormones in genetically susceptible subjects.

CONCLUSIONS

Variation in CYP11B2 and CYP11B1 associates with chronic up-regulation of the HPA axis. These novel data support the suggestion that chronic aldosterone excess, in genetically susceptible individuals, may be a consequence of increased ACTH drive to the adrenal and identify novel molecular mechanisms that may lead to the development of hypertension within the general population.

Prolonged human chorionic gonadotrophin stimulation as a tool for investigating and managing undescended testes

OBJECTIVE

To observe the outcome in a group of children with undescended testes (UDT) given prolonged human chorionic gonadotrophin (hCG) stimulation as part of their management.

STUDY DESIGN

Retrospective review of 16 prepubertal boys given intramuscular hCG, 1500 U, on Days 1, 2 and 3 and then twice a week for 2 weeks with assessment of serum testosterone (T), SHBG, dihydrotestosterone (DHT) and androstenedione (A) on Days 1, 4 and 22.

RESULTS

In seven boys (44%), peak rise in T was by Day 4; in 5 boys (31%), the rise was by Day 22 and in the remainder, serum T stayed low. The median Day1 testosterone : androstenedione (T : A) ratio rose from 0.4 (range 0.2-1.5) to 1.7 (range 0.2-5.3) at Day 4 (P < 0.05) with no further rise by Day 22. The median dihydrotestosterone : testosterone ratio (DHT : T) at Day 1 and Day 4 remained unchanged. SHBG levels were more likely to be lower at Day 22 than at Day 4. The mean testosterone : SHBG (T : SHBG) ratio as a marker of androgen sensitivity was 0.2 (1SD 0.1). Bilateral testicular descent deemed immediate surgery unnecessary in 3 out of 15 (20%) boys where outcome data were available.

CONCLUSION

Whilst a 3-day hCG stimulation regimen may exclude 17beta-hydroxysteroid dehydrogenase-3 and 5alpha-reductase deficiencies, some boys with cryptorchidism may require more prolonged stimulation to assess androgen production and sensitivity. The possibility that this regimen leads to a reduced need for orchidopexy requires further exploration.

Sentinel lymph node mapping of breast cancer via intradermal administration of Lymphoseek

Lymphoseek is a molecular imaging agent specifically designed for sentinel lymph node (SLN) mapping. We conducted a Phase I trial which measured the injection site clearance and SLN accumulation after a single intra dermal injection of Lymphoseek or [99mTc]sulfur colloid protocol. Ten patients with breast cancer participated in this study. Five patients received an intradermal administration of 1.0 nmol of 99mTc-labeled Lymphoseek and five patients received an intradermal administration of filtered [99mTc]sulfur colloid (fTcSC). Lymphoseek exhibited a significantly (P<.001) faster injection site clearance than fTcSC. The mean Lymphoseek clearance half-time was 2.61+/-0.72 h compared to 24.1+/-17.7 h for fTcSC. The mean SLN uptake of Lymphoseek (1.1+/-.5%) and fTcSC (2.5+/-4.9%) was statistically equivalent (P=.28). When an intra dermal injection was employed, Lymphoseek demonstrated faster injection site clearance than fTcSC.

Bilaterally symmetric juvenile fibroadenomas and tubular breast deformity in a prepubescent girl

Juvenile fibroadenomas are rare and usually not associated with other disease processes. We report the first known case of bilateral juvenile fibroadenomas in conjunction with tubular breast deformity in a prepubescent girl.

Variability in hydrocortisone plasma and saliva pharmacokinetics following intravenous and oral administration to patients with adrenal insufficiency

OBJECTIVE

The best method for determining hydrocortisone replacement therapy is not well defined. This study aimed to assess interindividual variability in cortisol pharmacokinetics and to investigate whether measurement of salivary cortisol provides a useful alternative to plasma concentration measurements.

DESIGN

Intravenous (IV) and oral crossover.

PATIENTS

Twenty-seven patients with primary or secondary adrenal insufficiency who had been on stable replacement therapy for at least 3 months.

MEASUREMENTS

Plasma and salivary concentrations of cortisol were measured up to 8 h following administration of hydrocortisone.

RESULTS

After IV administration, Cmax ranged from 715 to 8313 nmol/l, area under the curve (AUC) from 1112 to 12 177 nmol h/l and cortisol clearance had a median (range) of 0.267 (0.076-0.540) l/h/kg. After oral administration, Cmax ranged from 422 to 1554 nmol/l, AUC 1081-5471 nmol h/l and oral clearance had a median (range) of 0.267 (0.081-0.363) l/h/kg. There was no clear relationship between paired saliva and plasma cortisol concentrations after IV or oral dosing. Plasma and salivary AUC(2-8 h) after IV administration were highly correlated (r2 = 0.77) but differences between predicted and measured plasma AUCs ranged from 3% to 90%. There was a poor correlation between plasma and saliva AUC(2-6 h) after oral administration (r2 = 0.16).

CONCLUSIONS

The wide interindividual variability in plasma and salivary profiles of cortisol following the administration of IV and oral hydrocortisone to patients with adrenal insufficiency and the poor correlation between salivary and plasma measurements suggest that salivary cortisol measurements cannot be used for individual hydrocortisone dosage adjustment.

Endogenous corticosteroid biosynthesis in subjects after bilateral adrenalectomy

OBJECTIVE

Corticosteroids can be synthesized in extra-adrenal tissues but the contribution of this to circulating levels in humans is not known. Previous in vitro studies suggest that the 'hybrid' corticosteroid 18-oxocortisol (18-oxoF) is produced from cortisol by aldosterone synthase. We looked for evidence of extra-adrenal production of this and other corticosteroids in 10 subjects stable on long-term glucocorticoid replacement following bilateral adrenalectomy.

METHODS

In phase 1, patients were maintained on cortisol alone (30 mg/day), in phase 2 dexamethasone (2 mg/day), and in phase 3, both cortisol and dexamethasone. Each phase lasted 3 days.

MEASUREMENTS

On the last day of each phase, 24-h urine collection was performed for analysis of steroid metabolite excretion [using gas chromatography-mass spectrometry (GCMS)] and plasma aldosterone and renin were measured (by radioimmunoassay).

RESULTS

Cortisol metabolite excretion rate [tetrahydrocortisone (THE) + tetrahydrocortisol (THF) + allotetrahydrocortisol (aTHF)] fell from 9169 nmol/24 h in phase 1 to 22 nmol/24 h in phase 2, rising to 6843 nmol/24 h in phase 3. Tetrahydroaldosterone (THAldo) excretion was readily detectable and did not alter significantly between phases (26.5, 23.5 and 28.5 nmol/24 h, respectively; P = 0.474). 18-Hydroxycortisol (18-OHF) excretion was easily detectable in phases 1 and 3 (252.5 and 212 nmol/24 h), falling in phase 2 (12 nmol/24 h). 18-oxoF excretion rates were lower but followed a similar pattern (1.62, 0.085 and 1.785 nmol/24 h in phases 1, 2 and 3, respectively).

CONCLUSIONS

Significant levels of adrenal steroids are found in adrenalectomized subjects. We speculate that this occurs at extra-adrenal sites or in residual adrenal cortex tissue in an ACTH-independent manner. Our data suggest that aldosterone synthase, acting on cortisol, is the source of 18-oxoF and 18-OHF in these subjects. Further studies of corticosteroid production within adrenalectomized subjects, looking for evidence of adrenal regrowth or residual adrenal tissue, are justified.

Lymphoseek: a molecular imaging agent for melanoma sentinel lymph node mapping

BACKGROUND

Lymphoseek is a molecular imaging agent specifically designed for sentinel lymph node mapping. We conducted a phase I clinical trial in which Lymphoseek was compared with filtered [(99m)Tc]sulfur colloid (fTcSC) for melanoma sentinel lymph node detection.

METHODS

Twenty-four patients (33-81 years) with melanoma participated in this study. Four groups of six patients received an intradermal administration (.5 mCi) of 1.0, 5.0, or 10.0 nmol of (99m)Tc-labeled Lymphoseek or filtered [(99m)Tc]sulfur colloid. The injection site clearance was monitored by nuclear imaging for 3 hours. Lymph nodes obtained by gamma-guided biopsy (4.0-8.7 hours after injection) were assayed for radioactivity. Clinical chemistry values were monitored (before injection, before surgery, and 4 and 24 hours), and whole-body scans were acquired at 1 and 12 hours after injection.

RESULTS

Lymphoseek exhibited a significantly (P < .001) faster injection site clearance at all dose levels. The mean Lymphoseek clearance half-time was 2.17 +/- .96 hours (n = 18) compared with 14.7 +/- 6.3 hours for fTcSC (n = 6). The mean sentinel lymph node uptakes of Lymphoseek (.73% +/- .94%) and fTcSC (.85% +/- 1.19%) were statistically equivalent (P = .68). Lymphoseek exhibited a lower mean number of sentinel lymph nodes per basin (1.6) than fTcSC (1.9). No adverse events were observed, nor were any clinically significant alterations in laboratory parameters. Radiation absorbed doses were lower than filtered [(99m)Tc]sulfur colloid.

CONCLUSIONS

The molecular imaging agent Lymphoseek demonstrated faster injection site clearance and equivalent primary sentinel node uptake when compared with filtered [(99m)Tc]sulfur colloid.

Molecular targeting of the lymphovascular system for imaging and therapy

Progress toward targeting cancer cells is a multi-disciplinary endeavor. In addition to the surgical and oncology specialties, radiologists collaborate with mathematicians, computer scientists, and physicists, in a constant effort to incrementally improve upon the current imaging modalities. Recently, radiologists have formed collaborations with molecular biologists and chemists in order to develop molecular agents that target cancer cells via receptor-substrate or specific physiochemical interactions. In this review, we summarize selected efforts toward molecular targeting of the lymphovascular system. Standard imaging modalities, positron emission tomography, single photon emission tomography, and ultrasound, are reviewed as well as, the targeted introduction of substances for endolymphatic therapy. We also review the current status of sentinel lymph node mapping with radiocolloids and the application of molecular targeting for the development of a radiopharmaceutical specifically designed for sentinel lymph node mapping.

Undetectable salivary testosterone in young women with premature ovarian failure

BACKGROUND

The extent of androgen deficiency in young women with premature ovarian failure (POF) is unclear.

AIM

Cross-sectional study of androgen status in young women with POF.

PATIENTS

Twenty women with POF: six had Turner syndrome (group A); eight had iatrogenic POF either secondary to bilateral oophorectomy or treatment of malignancy (group B); and six had idiopathic POF (group C). The median age was 30.5 years (range 19-39); in groups B and C the median duration of ovarian failure was 10.0 years (range 1-35).

METHODS

After a 2-month wash-out period without sex steroid replacement (SSR), serum testosterone (T), androstenedione (A4), dehydroepiandrosterone (DHEAS), SHBG, salivary testosterone (SalT) and the free androgen index [FAI = (serum T/SHBG) x 100] were measured.

RESULTS

Median serum A4 was 4.6 nmol/l (10th, 90th centiles, 3.6, 5.1) and DHEAS was 3.2 micromol/l (10th, 90th centiles, 2.3, 9.3). Although median serum T was relatively low at 1.4 nmol/l (10th, 90th centiles, 1.1, 1.7), median SHBG was also low at 34 nmol/l (10th, 90th centiles 22.2, 67.5) and the median calculated FAI was within the normal range at 3.7 (10th, 90th centiles, 2.3, 7.0). However, SalT was undetectable in almost all subjects in the three groups of POF.

CONCLUSIONS

Serum T and SHBG are relatively low in young women with POF and their FAI is therefore within the normal range. However, SalT, which measures free testosterone, is consistently low to undetectable in these young women with POF. The reliability of the FAI as a marker of androgen deficiency remains questionable.

Minimally invasive sentinel lymph node mapping of the pig colon with Lymphoseek

BACKGROUND

Minimally invasive surgery and sentinel node mapping are being utilized increasingly in colon cancer surgery. Making these techniques efficient and easy to perform will be essential for the future of this and other gastrointestinal operations. The purpose of this study was to test a new laparoscopic gamma detection probe for minimally invasive sentinel node mapping of the colon, while utilizing Lymphoseek, a radiopharmaceutical specifically designed for sentinel lymph node (SLN) detection.

METHODS

Eight anesthetized pigs received an endoscopic co-injection of Lymphoseek and Isosulfan Blue in the colon. The laparoscopic gamma detector, inserted via a 12-mm trocar, was used to identify radioactive sentinel lymph nodes. The reliability of the side-viewing probe was tested using a radioactive source. All blue and radioactive lymph nodes were excised and the signal-to-background ratio (S/B) and percent of injected dose (%ID) were measured.

RESULTS

The probe was easy to maneuver and led to efficient visualization of the radioactive node. The side port allowed for better distinction between injection site scatter and sentinel node activity. The reliability of the probe was validated by an identification rate of 97%. At least one SLN was detected for each pig; two SLNs were detected in two pigs. All SLNs were stained blue. The SLN S/B ranged from 38 to 315 and the %ID ranged from 0.06% to 2.01%. Sentinel nodes were found within 10 minutes.

CONCLUSIONS

Minimally invasive sentinel node mapping with the radiopharmaceutical Lymphoseek and a side-viewing gamma detector yielded high S/B and directionality for accurate mapping of gastrointestinal sentinel lymph nodes within minutes of radiotracer administration.

A preclinical study of prostate sentinel lymph node mapping with [99mTC]diethylenetetramine pentaacetic acid-mannosyl-dextran

PURPOSE

SLN identification could improve the pathological staging of prostate cancer. Prior SLN studies have been compromised by delayed radiotracer uptake rates and significant diffusion rates out of the sentinel nodes. Lymphoseek is a new radiopharmaceutical specifically designed for SLN mapping. It shows rapid and sustained SLN uptake.

MATERIALS AND METHODS

We investigated the use of Lymphoseek for prostate SLN mapping by measuring SLN uptake in 12 anesthetized pigs. The prostate was injected with 0.05 ml of a 1:1 volume per volume mixture of Lymphazurin and 1.0 mCi Lymphoseek (1 nmole). Within 5 to 19 minutes the pelvic lymph nodes were dissected and assayed with a gamma probe. A lymph node was considered a sentinel node if it had count rates that exceeded 10 times the background count. We calculated the percent of injected dose of each lymph node excised and the prostate gland.

RESULTS

A total of 35 SLNs were identified in the 12 studies. Of the SLNs 81% were located outside of the obturator fossa in this pig model. The SLN percent of injected dose was 0.05% to 7.75% (mean +/- 1 SD 1.74% +/- 1.92%). The mean percent of injected dose in the prostate was 27% +/- 12%. There was no correlation between the side of SLN and the lobe injected.

CONCLUSIONS

After prostate administration of Lymphoseek pelvic SLNs attain high signal-to-background ratios within 10 minutes. This property should permit intraoperative injection and SLN mapping without significantly adding to the duration of prostatectomy. A phase I clinical trial has been initiated, which will later incorporate minimally invasive techniques.

Stability of housekeeping genes in alveolar macrophages from COPD patients

The stability of housekeeping genes is critical when performing gene expression studies. To date, there have been no studies that look at the stability of commonly used housekeeping genes in alveolar macrophages. Expression levels may be affected by culture, stimulation or disease severity. The present study investigated the expression level of 10 housekeeping genes and analysed the stability of their expression in alveolar macrophages from chronic obstructive pulmonary disease patients (n = 22) who were classified according to disease severity. Guanine nucleotide-binding protein, beta polypeptide 2-like 1 (GNB2L1), hypoxanthine phosphoribosyl transferase 1 (HPRT1) and ribosomal protein L32 (RPL32) were the most stably expressed in alveolar macrophages, irrespective of disease severity. There was no difference in the expression levels of 10 housekeeping genes between mild and moderate/severe patients. GNB2L1, HPRT1 and RPL32 were also stably expressed in alveolar macrophages cultured with no stimulation, or with interleukin-1beta, lipopolysaccharide or tumour necrosis factor-alpha stimulation. In conclusion, as fluctuations in the expression of some housekeeping genes were observed, including glyceraldehyde-3-phosphate dehydrogenase, it is recommended that guanine nucleotide binding protein, beta polypeptide 2-like 1 be used as a reference gene for alveolar macrophages in similar study designs, or that the stability of housekeeping genes be validated in alveolar macrophages prior to expression studies.

Breast imaging: a surgeon's prospective

Mammography, ultrasound, magnetic resonance imaging, positron emission tomography, gamma camera and intraoperative gamma detection, and computed tomography are employed in the diagnosis and treatment of breast cancer. This paper summarizes the role of each modality from the perspective of the physician responsible for management of the patient's care. An understanding of an imaging modality's current role can provide insights into the design of new applications and diagnostic agents. Moreover, knowledge of the mechanism by which each modality provides clinical information can guide the design of new imaging methods that complement and add certainty to the patient's management. The reader should note the lack of molecular information provided by the current imaging methods. The perspective concludes with a request for an imaging technique that can measure the biologic aggressiveness of a woman's cancer. The surgeon notes that basing the formation of an image on a molecular process would be compatible with current medical practice, which utilizes molecular concepts to base medical decisions. In addition, molecular imaging will enable rapid translation between basic science and medical practice.

The utility of three different methods for measuring urinary 18-hydroxycortisol in the differential diagnosis of suspected primary hyperaldosteronism

OBJECTIVE

Urine 18-hydroxycortisol (18-OHF) measurements are claimed to discriminate between primary hyperaldosteronism due to Conn's syndrome/adrenal adenoma or idiopathic bilateral adrenal hyperplasia (BAH), and also to identify cases of glucocorticoid-suppressible hyperaldosteronism (GSH). We have evaluated three urine 18-OHF methods using a panel of urine samples from patients with hypertension.

DESIGN

Clinical methods comparative study.

METHODS

Urine samples from patients with primary hyperaldosteronism due to either adenoma (n = 6), BAH (n = 6), GSH (n = 9), or essential hypertension (n = 38) were analysed without knowledge of the diagnosis using three different methods in different laboratories. These included 'in-house' radioimmunoassay (RIA), 'in-house' time-resolved fluorometric assay (DELFIA), and gas chromatography mass spectrometry (GC-MS).

RESULTS

The three assays showed good correlation, but there were large bias differences: RIA bias was greater than DELFIA which was greater than GC-MS. Discrimination between adenoma and BAH patients was best for the DELFIA method, with no overlap between results for these two groups. All three methods gave significantly elevated results for the GSH group compared with the BAH and essential hypertension groups. No assay distinguished BAH from essential hypertension.

CONCLUSION

Measurement of urine 18-OHF may be a useful additional test in the differential diagnosis of primary hyperaldosteronism. The clinical diagnostic value of urinary 18-OHF measurements is method-dependent with the DELFIA assay having the best discriminatory value.