TY - JOUR
T1 - Mainly the younger hypothyroid patients are referred to hospital--evidence for referral bias
AU - Carlé, Allan
AU - Laurberg, Peter
AU - Pedersen, Inge Bülow
AU - Knudsen, Nils
AU - Perrild, Hans
AU - Ovesen, Lars
AU - Rasmussen, Lone Banke
AU - Jørgensen, Torben
PY - 2009
Y1 - 2009
N2 - OBJECTIVE: Studies of hypothyroidism are often based on patients referred to hospital. It is unknown, to what extent such studies are referral biased. Thus, the aim of the present study was to evaluate the magnitude of selection bias in a study of patients newly diagnosed with hypothyroidism. STUDY DESIGN AND SETTING: A computer-based system linked to laboratory databases identified patients with incident overt hypothyroidism (n=346) from 1997 to 2000 in Aalborg, Denmark. An electronic patient administrative system identified patients referred to Department of Endocrinology, Aalborg Hospital. Among patient characteristics recorded at the time of diagnosis-age, gender, nosological subgroup of hypothyroidism, thyroid stimulating hormone (TSH), total thyroxine (T4), total triiodothyronine (T3), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), and calendar year--we searched for predictors of referral state. RESULTS: Of all hypothyroid patients, 86 (25%) were referred to our endocrine unit. The referred patients were younger (50.4 vs. 66.0 years, P<0.001), had higher serum TSH (53.6 vs. 32.6 mU/L, P=0.002) and lower serum total T4 (37.0 vs. 44.0 nmol/L, P=0.03) compared with nonreferred patients. In a multivariate model, only less age (P<0.001) and serum total T4 (P=0.03) were statistically associated with referral state. CONCLUSION: Hypothyroid patients referred to a specialized hospital unit were younger and marginally more hypothyroid than nonreferred patients. Thus, referral bias should always be considered in hospital-based studies of hypothyroid patients.
AB - OBJECTIVE: Studies of hypothyroidism are often based on patients referred to hospital. It is unknown, to what extent such studies are referral biased. Thus, the aim of the present study was to evaluate the magnitude of selection bias in a study of patients newly diagnosed with hypothyroidism. STUDY DESIGN AND SETTING: A computer-based system linked to laboratory databases identified patients with incident overt hypothyroidism (n=346) from 1997 to 2000 in Aalborg, Denmark. An electronic patient administrative system identified patients referred to Department of Endocrinology, Aalborg Hospital. Among patient characteristics recorded at the time of diagnosis-age, gender, nosological subgroup of hypothyroidism, thyroid stimulating hormone (TSH), total thyroxine (T4), total triiodothyronine (T3), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), and calendar year--we searched for predictors of referral state. RESULTS: Of all hypothyroid patients, 86 (25%) were referred to our endocrine unit. The referred patients were younger (50.4 vs. 66.0 years, P<0.001), had higher serum TSH (53.6 vs. 32.6 mU/L, P=0.002) and lower serum total T4 (37.0 vs. 44.0 nmol/L, P=0.03) compared with nonreferred patients. In a multivariate model, only less age (P<0.001) and serum total T4 (P=0.03) were statistically associated with referral state. CONCLUSION: Hypothyroid patients referred to a specialized hospital unit were younger and marginally more hypothyroid than nonreferred patients. Thus, referral bias should always be considered in hospital-based studies of hypothyroid patients.
U2 - 10.1016/j.jclinepi.2008.06.016
DO - 10.1016/j.jclinepi.2008.06.016
M3 - Journal article
C2 - 18945587
SN - 0895-4356
VL - 62
SP - 446
EP - 451
JO - Journal of Clinical Epidemiology
JF - Journal of Clinical Epidemiology
IS - 4
ER -