Objective: To investigate the effect of temperature on first trimester free β-hCG and PAPP-A in serum during transportation.
Methods: Maternal blood was collected from 30 East Asian women attending for Down syndrome screening at the primary obstetrical site. The extracted serum was split into two equal aliquots, placed in identical thermally insulated pouches with a temperature data logger and shipped to the screening laboratory. An 800 g frozen ice pack was placed in one of the pouches. Free β-hCG and PAPP-A levels were determined in the 'Cooled' and 'Uncooled' serum samples using a DELFIA(®) Xpress analyzer. The proportion of 'Uncooled' samples not within 5% of the 'Cooled' sample marker level was assessed.
Results: The median age of subjects was 36 years, half were nulliparous and all were non-smokers. The assay stability ranged from 2.38% to 4.41%. The median total transport time from the obstetrical site to the laboratory was 17.37 h. Median recorded temperatures within the 'Cooled' pouch were significantly lower throughout the transportation of the samples (p < 0.0001). The median percentage change of free β-hCG and PAPP-A concentrations in 'Uncooled' samples relative to 'Cooled' samples were 2.72% (range 0.27-7.64%) and 1.10% (range 0.03%-4.29%), respectively. Free β-hCG concentrations differed by greater than 5% in eleven (37%) subjects.
Conclusions: Insulated packaging, cooling media and temperature monitoring devices may be needed as additional measures to determine, minimize and exclude effects of ambient temperature on serum marker levels especially when travelling times are long or ambient temperatures are high.