title: The impact of time of sample collection on the measurement of thyroid stimulating hormone values in the serum.
abstract: OBJECTIVE
  The aim of our research is to determine whether the time of blood sampling and fasting of patients have an impact on TSH values.
  
  
  METHODS
  A total of 198 participants were enrolled in this study and classified into five groups: A--the first sample collection for TSH measurement was taken between 7:00 and 8:00 a.m. at fasting and the second after 140 min without food intake; B--between 7:00 and 8:00 a.m. at fasting and the second after 140 min with food intake; C--between 7:00 and 8:00 a.m. at fasting the previous day and the second one between 7:00 and 8:00 a.m. at fasting the following day; D--between 9:00 and 10:00 a.m. at fasting the previous day and the second one between 9:00 and 10:00 a.m. at fasting the following day, and E--between 9:00 and 10:00 a.m. at fasting the previous day and the second one between 7:00 and 8:00 a.m. on the following day. Serum TSH concentration was measured by electrochemiluminescence immunoassay (ECLIA, Roche Diagnostics, Mannheim, Germany).
  
  
  RESULTS
  TSH values (mIU/L) were in group A: 2.50 (2.20-2.81) first samples, 1.74 (1.52-1.96) second samples, p<0.001; B: 2.11 (1.52-2.72) first samples, 1.56 (1.13-1.81) second samples, p<0.001; C: 2.60 (2.28-2.91) first samples, 2.23 (1.92-2.53) second samples, p<0.001; D: 1.80 (1.48-2.11) first samples, 1.77 (1.44-2.09) second samples, p<0.597; and E: 1.32 (1.11-2.16) first samples, 1.67 (1.48-2.93) second samples, p<0.001.
  
  
  CONCLUSIONS
  The time of sample collection must be standardised for the purpose of standardisation and harmonisation of TSH measurements.
authors: University Hospital Clinical Centre Banja Luka, Banja Luka, Republic of Srpska, Bosnia and Herzegovina. Electronic address: bodamirjanic@blic.net.
authors: Bosa
authors: B
authors: Mirjanic-Azaric
authors: University Hospital Clinical Centre Banja Luka, Banja Luka, Republic of Srpska, Bosnia and Herzegovina.
authors: Tanja
authors: T
authors: Stojakovic-Jelisavac
authors: University Hospital Clinical Centre Banja Luka, Banja Luka, Republic of Srpska, Bosnia and Herzegovina.
authors: Blazenko
authors: B
authors: Vukovic
authors: Health Centre Laktasi, Laktasi, Republic of Srpska, Bosnia and Herzegovina.
authors: Darja
authors: D
authors: Stojanovic
authors: Medical Faculty, University of Banja Luka, Banja Luka, Bosnia and Herzegovina.
authors: Milorad
authors: M
authors: Vujnic
authors: Medical Faculty, University of Banja Luka, Banja Luka, Bosnia and Herzegovina.
authors: Snezana
authors: S
authors: Uletilovic
mesh_terms: D000328:Adult; D002940:Circadian Rhythm / Q000502:physiology*; D005215:Fasting; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D013048:Specimen Handling / Q000592:standards*; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D013997:Time Factors
chemical_list: D013972:Thyrotropin; D013974:Thyroxine
keywords: Thyroid stimulating hormone; Time of sample collection