Stability of Progranulin Under Pre-Analytical Conditions in Serum and Cerebrospinal Fluid

Abstract

Abstract. 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.

CSF progranulin increases in the course of Alzheimer's disease and is associated with sTREM 2, neurodegeneration and cognitive decline

“…The mean CSF PGRN level of our MSD‐based assay (1,007 pg/ml) was similar to that published with other assays (Huchtemann et al , ; Zhou et al , ; Berghoff et al , ; Meeter et al , ; Kimura et al , ; Schreiber et al , ), albeit lower than those measured by the more widely used commercial assay from Adipogen (Ghidoni et al , ; De Riz et al , ; Vercellino et al , ; Nicholson et al , ; Morenas‐Rodríguez et al , ; Feneberg et al , ; Molgaard et al , ; Willemse et al , ; Wilke et al , ). We therefore compared our MSD‐based ELISA with that from Adipogen (cat.…”

Progranulin Levels in Plasma and Cerebrospinal Fluid in Granulin Mutation Carriers

“…It was recently published that more commonly used PGRN ELISA kits (Adipogen and R&D) detected CSF PGRN in non- GRN carriers only at the lower detection range of the kits [ 24 ]. Because CSF PGRN of GRN carriers is at least 50% lower, we opted for the more sensitive protocol of Biovendor.…”

Fluid biomarkers in frontotemporal dementia: past, present and future

“…Lastly, the majority of studies have used a small set of (non-fully validated) commercially available ELISAs to measure progranulin concentrations so far (e.g. Adipogen, R+D, Biovendor), and whilst concentrations seem highly correlated between assays 46 , absolute levels are different. Although the epitopes detected by the capture and detection antibodies are not known (or available) for these assays, the high correlation suggests that they may well measure similar forms of progranulin but that they have not been standardised to each other: a certified reference material and an external quality control programme for progranulin would solve this issue and would allow for standardisation of reference and decision limits across assays and laboratories.…”