Growth hormone response during oral glucose tolerance test: the impact of assay method on the estimation of reference values in patients with acromegaly and in healthy controls, and the role of gender, age, and body mass index. Export

@article{citeulike:3563423, abstract = {CONTEXT: Besides the measurement of IGF-I, GH suppression during an oral glucose tolerance test is recommended to assess the biochemical status in acromegaly. However, the development of highly sensitive and specific GH assays necessitates a critical reevaluation of criteria for diagnosis and follow-up of disease activity. OBJECTIVE: Our objective was to evaluate the between-method discrepancies in GH determinations by different immunoassays considering further confounders like age, gender, and body mass index (BMI). DESIGN, SUBJECTS, AND METHODS: We measured GH during a 75-g oral glucose tolerance test in 46 acromegaly patients (18 controlled, 28 uncontrolled; 19 men; 31-63 yr; BMI 26.4 +/- 0.4 kg/m(2)) and 213 healthy subjects (66 men; 20-76 yr; BMI 30 +/- 0.5 kg/m(2)), using three different commercially available assays [Immulite (Diagnostic Products Corp., Los Angeles, CA), Nichols (Nichols Institute Diagnostika GmbH, Bad Vilbel, Germany), and Diagnostic Systems Laboratories (Sinsheim, Germany)] that were calibrated against the recently recommended GH standards. RESULTS: Results from all assays strongly correlated (r = 0.8-0.996; P < 0.0001). However, the results obtained with the Immulite assay were, on average, 2.3-fold higher than those obtained with Nichols and 6-fold higher than those obtained with Diagnostic Systems Laboratories. Using cutoff limits of 1 microg/liter (Immulite) and 0.5 microg/liter (Nichols) identified 95\% of patients with active disease and 78-80\% of patients in remission. Basal and nadir GH levels were significantly higher in females than in males (Immulite 2.2 +/- 0.28 microg/liter vs. 0.73 +/- 0.15 microg/liter and 0.16 +/- 0.01 microg/liter vs. 0.08 +/- 0.01 microg/liter; P < 0.001, respectively). In multiple regression analysis, age, BMI, and gender were predictors for basal and nadir GH levels. CONCLUSION: Postglucose GH-nadir values are assay, gender, age, and BMI specific, indicating the need of individual cutoff limits for each assay.}, author = {Arafat, A. M. and M\"{o}hlig, M. and Weickert, M. O. and Perschel, F. H. and Purschwitz, J. and Spranger, J. and Strasburger, C. J. and Sch\"{o}fl, C. and Pfeiffer, A. F.}, citeulike-article-id = {3563423}, citeulike-linkout-0 = {http://dx.doi.org/10.1210/jc.2007-2084}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/18171702}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=18171702}, comment = {The measurement of growth hormone (GH) in serum has been useful not only for the diagnosis of growth hormone deficiency (GHD), but also acromegaly. Use of different assays for measurement of GH have been accepted as interchangeable in interpreting the results. Cut off points for stimulation tests (GHD) and suppression tests (acromegaly) have been used to diagnose and follow patients. Use of the oral glucose tolerance test in acromegaly has been accepted using a nadir cutoff point of less than 1 ng/ml regardless of assay for the diagnosis of this disease. In this article Arafat and colleagues looked at split samples of blood taken from healthy and acromegalic patients for analysis using three different assays; the three commercially available assays compared were Immulite Diagnostic products Corp., Los Angeles CA, Nichols (Nichols Institute Diagnostika GMbh, Bad Vilbel, Germany) and Diagnostic systems Laboratories (Sinsheim, Germany). The Immulite and the Nichols assays were calibrated against the same standard (IS 98/574), and Diagnostic Systems assay used the IS 88/624 standard. The results were quite surprising and disturbing. The authors found the Immulite assay results were 2.3-fold higher than those obtained with the Nichols and 6-fold higher than those obtained with the Diagnostic Systems Laboratories. Basal and nadir GH levels after glucose were significantly higher in females than in males. In multiple regression analysis, age, BMI and gender were predictors for basal and nadir GH levels. These findings suggest that not only should gender and BMI be considered in interpreting GH responses to oral glucose in acromegaly, but now assay variability as well. These findings also suggest that GH responses to oral glucose may not be as reliable to diagnose patients with acromegaly and that using serum IGF-1 may be more clinically relevant. Needless to say the clinician must be familiar with the assay used by the clinical lab he or she is using in addition to clinical findings and the clinical context. Further work must be done to confirm these studies and to establish acceptable cutoff points with the different commercial assays avaiable. David M. Cook}, doi = {10.1210/jc.2007-2084}, issn = {0021-972X}, journal = {The Journal of clinical endocrinology and metabolism}, keywords = {acromegaly, diagnosis, r-gh}, month = {April}, number = {4}, pages = {1254--1262}, posted-at = {2008-11-18 01:07:34}, priority = {2}, title = {Growth hormone response during oral glucose tolerance test: the impact of assay method on the estimation of reference values in patients with acromegaly and in healthy controls, and the role of gender, age, and body mass index.}, url = {http://dx.doi.org/10.1210/jc.2007-2084}, volume = {93}, year = {2008} }

TY - JOUR ID - citeulike:3563423 L3 - citeulike-article-id:3563423 N2 - CONTEXT: Besides the measurement of IGF-I, GH suppression during an oral glucose tolerance test is recommended to assess the biochemical status in acromegaly. However, the development of highly sensitive and specific GH assays necessitates a critical reevaluation of criteria for diagnosis and follow-up of disease activity. OBJECTIVE: Our objective was to evaluate the between-method discrepancies in GH determinations by different immunoassays considering further confounders like age, gender, and body mass index (BMI). DESIGN, SUBJECTS, AND METHODS: We measured GH during a 75-g oral glucose tolerance test in 46 acromegaly patients (18 controlled, 28 uncontrolled; 19 men; 31-63 yr; BMI 26.4 +/- 0.4 kg/m(2)) and 213 healthy subjects (66 men; 20-76 yr; BMI 30 +/- 0.5 kg/m(2)), using three different commercially available assays [Immulite (Diagnostic Products Corp., Los Angeles, CA), Nichols (Nichols Institute Diagnostika GmbH, Bad Vilbel, Germany), and Diagnostic Systems Laboratories (Sinsheim, Germany)] that were calibrated against the recently recommended GH standards. RESULTS: Results from all assays strongly correlated (r = 0.8-0.996; P < 0.0001). However, the results obtained with the Immulite assay were, on average, 2.3-fold higher than those obtained with Nichols and 6-fold higher than those obtained with Diagnostic Systems Laboratories. Using cutoff limits of 1 microg/liter (Immulite) and 0.5 microg/liter (Nichols) identified 95% of patients with active disease and 78-80% of patients in remission. Basal and nadir GH levels were significantly higher in females than in males (Immulite 2.2 +/- 0.28 microg/liter vs. 0.73 +/- 0.15 microg/liter and 0.16 +/- 0.01 microg/liter vs. 0.08 +/- 0.01 microg/liter; P < 0.001, respectively). In multiple regression analysis, age, BMI, and gender were predictors for basal and nadir GH levels. CONCLUSION: Postglucose GH-nadir values are assay, gender, age, and BMI specific, indicating the need of individual cutoff limits for each assay. IS - 4 JF - The Journal of clinical endocrinology and metabolism SN - 0021-972X EP - 1262 TI - Growth hormone response during oral glucose tolerance test: the impact of assay method on the estimation of reference values in patients with acromegaly and in healthy controls, and the role of gender, age, and body mass index. VL - 93 SP - 1254 KW - acromegaly KW - diagnosis KW - r-gh N1 - The measurement of growth hormone (GH) in serum has been useful not only for the diagnosis of growth hormone deficiency (GHD), but also acromegaly. Use of different assays for measurement of GH have been accepted as interchangeable in interpreting the results. Cut off points for stimulation tests (GHD) and suppression tests (acromegaly) have been used to diagnose and follow patients. Use of the oral glucose tolerance test in acromegaly has been accepted using a nadir cutoff point of less than 1 ng/ml regardless of assay for the diagnosis of this disease. In this article Arafat and colleagues looked at split samples of blood taken from healthy and acromegalic patients for analysis using three different assays; the three commercially available assays compared were Immulite Diagnostic products Corp., Los Angeles CA, Nichols (Nichols Institute Diagnostika GMbh, Bad Vilbel, Germany) and Diagnostic systems Laboratories (Sinsheim, Germany). The Immulite and the Nichols assays were calibrated against the same standard (IS 98/574), and Diagnostic Systems assay used the IS 88/624 standard. The results were quite surprising and disturbing. The authors found the Immulite assay results were 2.3-fold higher than those obtained with the Nichols and 6-fold higher than those obtained with the Diagnostic Systems Laboratories. Basal and nadir GH levels after glucose were significantly higher in females than in males. In multiple regression analysis, age, BMI and gender were predictors for basal and nadir GH levels. These findings suggest that not only should gender and BMI be considered in interpreting GH responses to oral glucose in acromegaly, but now assay variability as well. These findings also suggest that GH responses to oral glucose may not be as reliable to diagnose patients with acromegaly and that using serum IGF-1 may be more clinically relevant. Needless to say the clinician must be familiar with the assay used by the clinical lab he or she is using in addition to clinical findings and the clinical context. Further work must be done to confirm these studies and to establish acceptable cutoff points with the different commercial assays avaiable. David M. Cook AU - Arafat, AM AU - Möhlig, M AU - Weickert, MO AU - Perschel, FH AU - Purschwitz, J AU - Spranger, J AU - Strasburger, CJ AU - Schöfl, C AU - Pfeiffer, AF PY - 2008/04// UR - http://dx.doi.org/10.1210/jc.2007-2084 ER -