TY - JOUR
T1 - High Age Predicts Low Referral of Hyperthyroid Patients to Specialized Hospital Departments
T2 - Evidence for Referral Bias
AU - Carlé, Allan
AU - Pedersen, Inge Bülow
AU - Perrild, Hans
AU - Ovesen, Lars
AU - Jørgensen, Torben
AU - Laurberg, Peter Marsvin
PY - 2013/12/1
Y1 - 2013/12/1
N2 - Background: Hospital-based studies may be hampered by referral bias. We investigated how the phenomenon may influence studies of hyperthyroid patients. Methods: By means of a computer-based linkage to the laboratory database and subsequent detailed evaluation of subjects with abnormal test results, we prospectively identified all 1148 patients diagnosed with overt hyperthyroidism in a four-year period in and around Aalborg City, Denmark. Each patient was classified according to nosological type of hyperthyroidism. We studied the referral pattern of patients to local hospital units, and analyzed how referral depended on subtype of disease, sex, age, and degree of biochemical hyperthyroidism. Results: In a 4-year period, 1032 hyperthyroid patients were diagnosed at primary care offices, and 435 of these (42.2%) were referred to specialized units, 92 patients had hyperthyroidism diagnosed in other hospital departments (referral: 43, 46.7%), and 24 patients had hyperthyroidism diagnosed at the specialized unit after referral for other diseases. Patients suffering from Graves' disease (GD; n=474, median age=65.8 years) were referred more often (odds ratio=1.7 [95% confidence interval 1.3-2.2]) than those diagnosed with multinodular toxic goiter (MNTG; n=525, median age=74.6 years). Higher age was associated with less referral of patients suffering from MNTG (referred vs. nonreferred patients, 64.0 vs. 77.4 years, p<0.001) and GD (43.9 vs. 56.4 years, p<0.001), whereas GD patients referred to a hospital had more severe biochemical hyperthyroidism (serum total triiodothyronine, 4.86 vs. 3.79 nmol/L; serum total thyroxine, 204 vs. 180 nmol/L; both p<0.001). Findings were confirmed in multivariate models reporting age as a significant predictor for referral in both GD and MNTG patients (both p<0.001). Among referred hyperthyroid patients (all combined), those aged up to 40 years (referral rate, 66.8%) were represented 11.6 (6.6-20.6) times more often than those aged 80 years and above (referral rate, 14.8%). Conclusions: Hyperthyroid patients referred to a specialized hospital unit were younger (GD+MNTG) and had more severe biochemical hyperthyroidism (GD) compared to nonreferred patients. Thus, referral bias may influence hospital-based studies of hyperthyroid patients, and may hamper external generalization of such studies. Whether the referral bias of hyperthyroid patients in Denmark can be generalized to other countries or cultures remains unknown.
AB - Background: Hospital-based studies may be hampered by referral bias. We investigated how the phenomenon may influence studies of hyperthyroid patients. Methods: By means of a computer-based linkage to the laboratory database and subsequent detailed evaluation of subjects with abnormal test results, we prospectively identified all 1148 patients diagnosed with overt hyperthyroidism in a four-year period in and around Aalborg City, Denmark. Each patient was classified according to nosological type of hyperthyroidism. We studied the referral pattern of patients to local hospital units, and analyzed how referral depended on subtype of disease, sex, age, and degree of biochemical hyperthyroidism. Results: In a 4-year period, 1032 hyperthyroid patients were diagnosed at primary care offices, and 435 of these (42.2%) were referred to specialized units, 92 patients had hyperthyroidism diagnosed in other hospital departments (referral: 43, 46.7%), and 24 patients had hyperthyroidism diagnosed at the specialized unit after referral for other diseases. Patients suffering from Graves' disease (GD; n=474, median age=65.8 years) were referred more often (odds ratio=1.7 [95% confidence interval 1.3-2.2]) than those diagnosed with multinodular toxic goiter (MNTG; n=525, median age=74.6 years). Higher age was associated with less referral of patients suffering from MNTG (referred vs. nonreferred patients, 64.0 vs. 77.4 years, p<0.001) and GD (43.9 vs. 56.4 years, p<0.001), whereas GD patients referred to a hospital had more severe biochemical hyperthyroidism (serum total triiodothyronine, 4.86 vs. 3.79 nmol/L; serum total thyroxine, 204 vs. 180 nmol/L; both p<0.001). Findings were confirmed in multivariate models reporting age as a significant predictor for referral in both GD and MNTG patients (both p<0.001). Among referred hyperthyroid patients (all combined), those aged up to 40 years (referral rate, 66.8%) were represented 11.6 (6.6-20.6) times more often than those aged 80 years and above (referral rate, 14.8%). Conclusions: Hyperthyroid patients referred to a specialized hospital unit were younger (GD+MNTG) and had more severe biochemical hyperthyroidism (GD) compared to nonreferred patients. Thus, referral bias may influence hospital-based studies of hyperthyroid patients, and may hamper external generalization of such studies. Whether the referral bias of hyperthyroid patients in Denmark can be generalized to other countries or cultures remains unknown.
U2 - 10.1089/thy.2013.0074
DO - 10.1089/thy.2013.0074
M3 - Journal article
C2 - 23745710
SN - 1050-7256
VL - 23
SP - 1518
EP - 1524
JO - Thyroid
JF - Thyroid
IS - 12
ER -