Diagnostic Accuracy of Dried Blood Spots Collected on HemaSpot HF Devices Compared to Venous Blood Specimens To Estimate Measles and Rubella Seroprevalence

Abstract

Fingerprick blood spotted onto filter paper offers an alternative to venous blood for use in population-based surveillance because it is comparatively inexpensive, acceptable, and easy to manage in the field. Prior studies have shown excellent agreement for immunoglobulin G (IgG) antibody detection from dried blood spots (DBS) and venous blood samples. However, much of this evidence is from high-income settings or laboratories where the samples were unlikely to be exposed to extreme temperatures and humidity, factors known to degrade DBS. We report the diagnostic accuracy of DBS collected using HemaSpot HF devices against venous sera in measuring measles- and rubella-specific IgG antibodies in a household serosurvey conducted in two districts in India. Paired serum and DBS samples collected by fingerprick were collected from women aged 15 to 50 years enrolled in a serosurvey in Palghar District of Maharashtra and Kanpur Nagar District of Uttar Pradesh in India. Specimen quality and volume were assessed in the laboratory. Samples were tested for antimeasles and antirubella IgG antibodies by an enzyme-linked immunosorbent assay (ELISA) (Euroimmun). Sensitivity of antibody detection by DBS was greater than 98%, and specificity was 90% and 98%, for measles and rubella IgG, respectively. Antibody concentrations were strongly correlated between paired specimens with adequate volume (measles R² = 0.94; rubella R² = 0.89). Although correlation was poor if DBS specimens had lower volumes, impact on qualitative results was minimal. This study showed DBS collected with HemaSpot HF devices can generate highly accurate results of measles- and rubella-specific IgG compared to sera in community-based surveys when protocols are optimized for DBS specimens. IMPORTANCE Dried blood spot (DBS) collection provides an easy, practical, and acceptable alternative to venous blood collection, especially for community-based studies, provided that results from DBS are accurate. We demonstrated high sensitivity and specificity for measles- and rubella-specific immunoglobulin G (IgG) with DBS collected via HemaSpot HF devices compared to serum samples. This is one of the largest community-based diagnostic accuracy studies of measles and rubella antibody testing with DBS and the first application we are aware of using HemaSpot HF device for measles and rubella serology. Results support the use of DBS in community-based serosurveillance.

Keywords: ELISA; India; diagnostic accuracy; dried blood spots; measles; rubella; serology.

FIG 1

Flowchart of participants. Abbreviation: DBS, dried blood spot. Footnote a, device unavailable due to stock out. Footnote b, fungal or bacterial growth observed at the time of testing, primarily from one site. The collection protocol was revised to reduce contamination risk. Footnote c, four devices were mislabeled, and results were excluded from analyses.

FIG 2

Intra-assay (A and C) and interassay (B and D) correlation of dried blood spot replicates, measles (top row) and rubella (bottom row). Contaminated, mislabeled, and extremely low volume samples were excluded. The red line indicates the line of equivalence. The dashed lines indicate equivocal thresholds (200 mIU/ml for measles and 8 IU/ml for rubella). Rsq, R².

FIG 3

Quantitative relationship in measles (A) and rubella (B) antibody detected in serum versus dried blood spot specimen by quality of specimen. Graphs were restricted to values below the highest calibrator of assays (5,000 mIU/ml for measles and 200 IU/ml for rubella). The dashed lines indicate equivocal and positive thresholds (equivocal, 200 mIU/ml for measles and 8 IU/ml for rubella; positive, 275 mIU/ml for measles and 11 IU/ml for rubella). Excessive volume DBS samples were grouped with adequate volume samples for scatterplot but were excluded for the purpose of calculating the R² among adequate samples (second row in inset box). The red line indicates the line of equivalence.

FIG 4

Mean of measles (A) and rubella (B) antibody concentrations plotted against the difference of serum versus dried blood spot. Vertical dashed lines indicate equivocal and positive thresholds (equivocal, 200 mIU/ml for measles and 8 IU/ml for rubella; positive, 275 mIU/ml for measles and 11 IU/ml for rubella). The gray dashed horizontal line indicates an absolute difference of 0. Black horizontal lines indicate the mean difference (solid line) and the limits of agreement (mean difference plus or minus 1.96 standard deviations of the difference; dashed lines). Excessive volume DBS samples were grouped with adequate volume samples.