title: Stability of procalcitonin at room temperature.
abstract: BACKGROUND
  The aim was to assess procalcitonin (PCT) stability after two days of storage at room temperature.
  
  
  METHODS
  Samples were collected from febrile children aged 7 to 92 days and were rapidly frozen after sampling. PCT levels were measured twice after thawing: immediately (named y) and 48 hours later after storage at room temperature (named x). PCT values were described with medians and interquartile ranges or by categorizing them into classes with thresholds 0.25, 0.5, and 2 ng/mL. The relationship between x and y PCT levels was analyzed using fractional polynomials in order to predict the PCT value immediately after thawing (named y') from x.
  
  
  RESULTS
  A significant decrease in PCT values was observed after 48 hours of storage at room temperature, either in median, 30% lowering (p < 0.001), or as categorical variable (p < 0.001). The relationship between x and y can be accurately modeled with a simple linear model: y = 1.37 x (R2 = 0.99). The median of the predicted PCT values y' was quantitatively very close to the median of y and the distributions of y and y' across categories were very similar and not statistically different.
  
  
  CONCLUSIONS
  PCT levels noticeably decrease after 48 hours of storage at room temperature. It is possible to pre- dict accurately effective PCT values from the values after 48 hours of storage at room temperature with a simple statistical model.
authors: Karen
authors: K
authors: Milcent
authors: Claire
authors: C
authors: Poulalhon
authors: Christelle Vauloup
authors: CV
authors: Fellous
authors: François
authors: F
authors: Petit
authors: Jean
authors: J
authors: Bouyer
authors: Vincent
authors: V
authors: Gajdos
mesh_terms: D015415:Biomarkers / Q000097:blood; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D005334:Fever / Q000097:blood*; D005615:Freezing; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015233:Models, Statistical; D011489:Protein Denaturation; D011498:Protein Precursors / Q000097:blood*; D055550:Protein Stability; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods*; D013696:Temperature; D013997:Time Factors
chemical_list: D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide