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Filter paper-based insulin-like growth factor assay
Anne K Jensen1, Carrie Coleman2, David Stokes2
1Division of Ophthalmology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania Perelman School of Medicine, Philadelphia.
Insights
This study validates a filter paper blood spot assay for insulin-like growth factor 1 (IGF-1), proving it reliable and feasible for retinopathy of prematurity (ROP) research. The method shows high accuracy and stability, supporting its use in clinical studies.
Area of Science:
- Biochemistry
- Pediatric Ophthalmology
- Clinical Diagnostics
Background:
- Insulin-like growth factor 1 (IGF-1) plays a crucial role in development and is implicated in retinopathy of prematurity (ROP).
- Accurate IGF-1 measurement is vital for ROP research, but traditional serum assays require venipuncture, posing challenges in neonates.
- Filter paper blood spot assays offer a less invasive alternative for sample collection and transport.
Purpose of the Study:
- To assess the validity, reliability, and feasibility of a filter paper blood spot assay for measuring IGF-1 in the context of ROP research.
- To determine the stability of IGF-1 on filter paper under various storage conditions.
- To evaluate the practical application of this assay in a cohort of premature infants undergoing ROP screening.
Main Methods:
- Blood samples from 45 healthy children were divided into serum and filter paper spots.
- IGF-1 levels were measured in both serum and blood spots using a commercial assay kit.
- Filter paper samples were stored under different time and temperature conditions to assess stability.
- Test-retest reliability was evaluated.
- Feasibility was assessed through collection and analysis of 817 filter card samples from 74 premature infants in a second cohort study.
Main Results:
- High intraclass correlation (0.97) was observed between blood spot and serum IGF-1 values, indicating excellent validity.
- Low mean differences confirmed good test-retest reliability.
- IGF-1 levels on filter paper remained stable for up to 25 days and across temperatures from 4°C to 37°C.
- Successful collection, transport, and assay of 817 filter card samples from premature infants demonstrated feasibility.
Conclusions:
- The filter paper blood spot assay for IGF-1 is a valid, reliable, and stable method for ROP research.
- This minimally invasive technique is feasible for large-scale sample collection and analysis in premature infants.
- The assay facilitates easier sample handling and transport, making it suitable for multicenter ROP studies and potentially for clinical diagnostics.
Abstract:
This study assessed validity, reliability, and feasibility of a filter paper blood spot insulin-like growth factor 1 (IGF-1) assay for retinopathy of prematurity (ROP) research. Blood samples were collected from 45 healthy children. Half of each sample was spun to obtain serum; half was applied to filter cards and stored for varying times and at different temperatures. IGF-1 assays were performed using a commercially available kit. Intraclass correlation between blood spot and serum IGF-1 values was high (0.97) for validity, and the mean differences were low for test-retest reliability. Time (up to 25 days) and temperature (4° C to 37° C) had no significant effect on sample stability. Feasibility was further assessed in a second cohort study of 74 premature infants being screened for ROP. A total of 817 filter card samples were successfully collected and transported to a central lab, where IGF-1 assays were successfully performed.
