Stability of Progranulin Under Pre-Analytical Conditions in Serum and Cerebrospinal Fluid.
Progranulin (PGRN) levels in blood and cerebrospinal fluid (CSF) are increasingly studied as potential markers for neurodegenerative disorders. We aimed to 1) characterize two commercially available PGRN ELISAs on several assay validation parameters, 2) assess the stability of PGRN in serum and CSF under pre-analytical conditions, and 3) compare stability in the two assays. Intra- and inter-assay variation, inter-lot variation, linearity, lower limit of detection, and kit correlations were assessed for the Adipogen and R&D PGRN ELISA kits. Blood and serum samples were experimentally exposed to ≤9 freeze/thaw cycles, delayed processing for ≤24 h at room temperature and 4°C, and to temperature stability tests for ≤3 weeks at -20°C, 4°C, room temperature, and 37°C. Both commercial PGRN ELISA kits showed acceptable ranges for intra- and inter-assay variation, where the R&D kit performed more accurate than the Adipogen kit, especially for inter-assay variation (intra-assay serum: 6.7 and 8.3%, respectively; inter-assay serum: 9.2 and 21.0%; intra-assay CSF: 3.6 and 12.0%; inter-assay CSF: 16.0 and 44.5%). Absolute serum PGRN concentrations were 1.9-fold higher in Adipogen than R&D (p < 0.001) and strongly correlated between both kits (ρ= 0.86, p < 0.0001) and CSF PGRN levels were on the borderline of detection in both kits. PGRN was typically stable under all pre-analytical conditions addressed, although two weeks at 37°C resulted in decreased PGRN concentrations in CSF, only when using the Adipogen kit. These results support further examination of PGRN as a potential marker in neurodegenerative diseases, since PGRN is stable in serum and CSF and can be measured using ELISA kits from several providers.
Clinical Chemistry, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.|Neurology and Alzheimer Center, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.
Eline A J
EA
Willemse
Clinical Chemistry, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.
Sisi
S
Durieux-Lu
Neurology and Alzheimer Center, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.|Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands.
Wiesje M
WM
van der Flier
Neurology and Alzheimer Center, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.
Yolande A L
YA
Pijnenburg
Clinical Chemistry, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.
Robert
R
de Jonge
Clinical Chemistry, Neuroscience Campus Amsterdam, VU University Medical Center Amsterdam, The Netherlands.
Charlotte E
CE
Teunissen
D015415:Biomarkers / Q000097:blood / Q000134:cerebrospinal fluid; D015925:Cryopreservation / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005215:Fasting / Q000097:blood / Q000134:cerebrospinal fluid; D005615:Freezing; D057180:Frontotemporal Dementia / Q000097:blood / Q000134:cerebrospinal fluid; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000097:blood* / Q000134:cerebrospinal fluid*; D016014:Linear Models; D000077153:Progranulins; D055550:Protein Stability; D015203:Reproducibility of Results; D013997:Time Factors
D015415:Biomarkers; C492314:GRN protein, human; D036341:Intercellular Signaling Peptides and Proteins; D000077153:Progranulins
Cerebrospinal fluid; ELISA; human progranulin protein; method comparison; pre-analytical variation; protein stability; serum