Biomedical subjects

Fidaa Ibrahim

Publications and source records attributed to Fidaa Ibrahim.

5 recordsLinked to original sources

PubMed2006

Diagnosis of adrenal insufficiency in severe sepsis and septic shock.

RATIONALE: Diagnosis of adrenal insufficiency in critically ill patients has relied on random or cosyntropin-stimulated cortisol levels, and has not been corroborated by a more accurate diagnostic standard. OBJECTIVE: We used the overnight metyrapone stimulation test to investigate the diagnostic value of the standard cosyntropin stimulation test, and the prevalence of sepsis-associated adrenal insufficiency. METHODS: This was an inception cohort study. MEASUREMENTS AND RESULTS: In two consecutive septic cohorts (n = 61 and n = 40), in 44 patients without sepsis and in 32 healthy volunteers, we measured (1) serum cortisol before and after cosyntropin stimulation, albumin, and corticosteroid-binding globulin levels, and (2) serum corticotropin, cortisol, and 11beta-deoxycortisol levels before and after an overnight metyrapone stimulation. Adrenal insufficiency was defined by postmetyrapone serum 11beta-deoxycortisol levels below 7 microg/dl. More patients with sepsis (31/61 [59% of original cohort with sepsis] and 24/40 [60% of validation cohort with sepsis]) met criteria for adrenal insufficiency than patients without sepsis (3/44; 7%) (p < 0.001 for both comparisons). Baseline cortisol (< 10 microg/dl), Delta cortisol (< 9 microg/dl), and free cortisol (< 2 microg/dl) had a positive likelihood ratio equal to infinity, 8.46 (95% confidence interval, 1.19-60.25), and 9.50 (95% confidence interval, 1.05-9.54), respectively. The best predictor of adrenal insufficiency (as defined by metyrapone testing) was baseline cortisol of 10 microg/dl or less or Delta cortisol of less than 9 microg/dl. The best predictors of normal adrenal response were cosyntropin-stimulated cortisol of 44 microg/dl or greater and Delta cortisol of 16.8 microg/dl or greater. CONCLUSIONS: In sepsis, adrenal insufficiency is likely when baseline cortisol levels are less than 10 microg/dl or delta cortisol is less than 9 microg/dl, and unlikely when cosyntropin-stimulated cortisol level is 44 microg/dl or greater or Delta cortisol is 16.8 microg/dl or greater.

Adrenal Insufficiency↗

PubMed2006

Unexpected serum parathyroid hormone profiles in some patients with primary hyperparathyroidism.

BACKGROUND: Third-generation parathyroid hormone (PTH) assays have been reported to measure only intact PTH(1-84), in contrast to second-generation assays, which also detect PTH(7-84) fragments. Higher PTH measurements were observed with third- than with second-generation PTH assays in a few patients with either severe primary hyperparathyroidism or parathyroid carcinoma. METHODS: We analyzed biological data [second- and third-generation PTH assays, 25-hydroxyvitamin D (25-OHD), calcium, and phosphate concentrations] obtained before and after surgery for 2 groups of patients selected from a large series of consecutive patients with primary hyperparathyroidism (PHPT): 7 female patients with surgically and histologically confirmed PHPT (group 1) and a matched group (group 2). RESULTS: For group 1 but not group 2, PTH concentrations measured by third-generation PTH assays before surgery were higher than those measured by the second-generation assays. Circulating 25-OHD, calcium, and phosphate concentrations were similar in both groups. In addition, PTH values measured with the third-generation PTH assays in group 1 decreased after surgery. CONCLUSIONS: Our results confirm that third-generation PTH assays do not measure only PTH(1-84). The frequency of this unexpected finding of markedly lower PTH concentrations than previously reported was approximately 5% in patients with PHPT without malignancy. We do not know whether the presence of this unexpected profile is predictive of malignancy.

Adult↗

PubMed2005

Serum bioavailable testosterone: assayed or calculated?

BACKGROUND: Bioavailable testosterone (BT), circulating testosterone not bound to sex hormone-binding globulin (SHBG), is thought to easily penetrate cells. We compared BT measurements obtained by assays with those obtained by calculation with different testosterone association constants. METHODS: We obtained sera from 2 groups of hypogonadal men [group 1 (G1), 1421 samples; group 2 (G2), 170 samples] and a group of healthy men [group 3 (G3), 109 samples]. We added minute doses of [3H]testosterone to the sera, precipitated the SHBG-bound fraction of testosterone with ammonium sulfate (50% saturation), and then assayed serum BT (ABT) as %BT x total. Calculated BT (CBT) was determined with theoretical association constants of testosterone for SHBG (Ks = 1 x 10(9) L/mol) and albumin (Ka = 3.6 x 10(4) L/mol) and paired optimal Ks and Ka values obtained by use of Microsoft Excel software. RESULTS: CBT calculated with theoretical constants differed from ABT by >30% in 85.7% (G1), 84.1% (G2), and 77.9% (G3) of samples, and the mean CBT/ABT ratios were 1.57 (G1), 1.85 (G2), and 1.50 (G3) in spite of fairly good correlations. CBT calculated with paired optimal K(s) and K(a) differed from ABT by <30% in 87.4% (G1), 87.5% (G2), and 97.5% (G3) of samples, and mean CBT/ABT ratios were 0.95-1.04. CONCLUSIONS: To obtain CBT values as close as possible to ABT, optimal paired association constants determined for each studied population must be used instead of the theoretical association constants. Considering the uncertainty of calculating BT, however, use of the ammonium sulfate precipitation method for determining BT is advisable.

Androgens↗

PubMed2005

Third- or second-generation parathyroid hormone assays: a remaining debate in the diagnosis of primary hyperparathyroidism.

BACKGROUND: Since the demonstration that the second-generation PTH assays, also called intact PTH assays, recognize a non-1-84 PTH fragment in addition to the intact 1-84 PTH, new PTH assays defined as third-generation assays have been commercialized. Two previous studies aimed at evaluating whether these third-generation PTH assays improved the diagnostic sensitivity for primary hyperparathyroidism (PHPT), but they yielded opposite results. METHODS: In the present study we compared two second-generation PTH assays (the total intact PTH assay from Scantibodies Laboratory, Inc., and the intact PTH assay from Nichols Institute Diagnostics) with two third-generation assays (the cyclase-activating PTH assay also from Scantibodies Laboratory and the bio-intact PTH assay from Nichols Institute) in a series of 145 consecutive PHPT patients operated in our endocrine surgery department over a 10-month period. A group of 74 healthy subjects served as controls. RESULTS: The diagnostic sensitivities for PHPT of the total intact, the intact, the cyclase-activating, and the bio-intact assays were 93.8%, 97.3%, 84.2%, and 89.0%, respectively, with 95% confidence intervals in the control groups of 10-46, 11-60, 8.4-34, and 9-41 ng/liter, respectively. CONCLUSION: Our findings demonstrate that the diagnostic sensitivities of second- and third-generation PTH assays are similar. Third-generation PTH assays do not therefore improve the diagnosis of elevated serum PTH levels in PHPT, although there are numerical differences among the values.

Aged↗

PubMed2003

Plasma 11beta-hydroxy-4-androstene-3,17-dione: comparison of a time-resolved fluoroimmunoassay using a biotinylated tracer with a radioimmunoassay using a tritiated tracer.

The plasma concentration of 11beta-hydroxy-4-androstene-3,17-dione (11beta) is very high in 21-hydroxylase deficiency, Cushing's syndrome, and hyperandrogenism of adrenal origin, and very low in congenital 11-hydroxylase deficiency and adrenal insufficiency. Thus, when plasma 4-androstenedione is elevated, it is useful to measure the plasma 11beta level in order to determine the adrenal or ovarian origin of the hyperandrogenism. To eliminate disadvantages related to the 11beta radioimmunoassay (RIA), which uses a tritiated tracer, as well as the high cost associated with scintillation proximity assay (SPA), we developed a non-isotopic 11beta assay that utilizes an 11beta-biotin conjugate synthesized in our laboratory to measure time-resolved fluorescence after addition of streptavidin-europium to microtitration wells. The analytical qualities of this assay are very similar to those of the radioimmunoassay using a tritiated tracer, and an extraction step followed by celite chromatography (which separates 11beta from interfering plasma steroids) prior to a final radioimmuno-competition step. The correlation coefficient between 11beta levels measured by time-resolved plasma 11beta fluoroimmunoassay (TR-FIA) and RIA was 0.965.Finally, the TR-FIA technique was more sensitive and of greater precision than the RIA method.

Androstenedione↗