Capillary blood sampling shows promise as an alternative to venipuncture in areas with limited resources to rapidly diagnose Ebola during a crisis situation, researchers who compared the two methods in an African population concluded. However, additional tests should be conducted to further prove its efficacy.
Study results were published in the journal Clinical Infectious Diseases. “Venous blood sampling requires trained and skilled medical personnel, bears high risk for needlestick injuries, and is especially difficult to perform with newborns and infants. Moreover, patients in African settings often refuse venipuncture due to cultural and religious beliefs,” the researchers wrote.
Capillary blood testing, which utilizes a fingerstick method, is less invasive than a venous test and doesn’t require a trained phlebotomist. “Moreover, capillary blood collection is the preferred method of blood specimen collection for newborns and infants,” they noted.
Researchers did a comparative analysis of venous and capillary blood collection methods at a treatment center in Guinea, the African country where the current Ebola virus outbreak originated.
Study participants included 53 patients suspected of Ebola virus disease (EVD) infections who sought care at the Ebola Treatment Centre in Guéckédou, Guinea, last summer. Researchers did a simultaneous comparison of venous and capillary blood samples from these patients, accumulating 120 samples in total. The RealStar Filovirus Screen RT-PCR Kit 1.0, a reliable reverse transcription polymerase chain reaction testing method, was used to analyze specimens.
While the capillary blood tests scored 100% on specificity and also yielded high sensitivity (86.8%), there were several instances in which these tests proved to be less sensitive than the venous tests, or produced slightly different results.
The 60 capillary blood samples yielded 33 positive and 27 negative results for Ebola, compared with 38 positive and 22 negative tests among the 60 venous samples. Although 5 of the capillary blood samples were found to be false-negative, the venous and capillary samples shared the same results in 55 of the samples.
“For the 55 capillary blood samples with identical results, 33 tested EVD positive and 22 tested EVD negative. In our study, no false-positive results were observed using capillary blood samples as a diagnostic specimen,” according to the study’s authors.
Sampling and collection processes, in addition to the virus’s stage of disease, could explain the differences in results between the two sampling methods. Researchers suggested additional studies on Ebola viral load in capillary blood, to more accurately evaluate the diagnostic results of these tests.
Overall, they concluded that capillary blood sampling would serve as a useful first-line method to screen large volumes of people during an outbreak. Venous blood samples in the meantime should remain the core standard for RT-PCR-based Ebola testing. “Suspected cases testing negative for EVD using capillary blood samples should be additionally tested using venous blood samples…Similarly, at present, venous-derived blood is recommended for testing patients during the convalescent phase to enhance decision making on their discharge and reintroduction in the community,” the article stated.