A test that uses a single drop of dried blood to detect HIV, hepatitis B virus, and HCV has been validated and is now in use in some high-risk settings in Denmark, according to research presented at the annual European Congress of Clinical Microbiology & Infectious Diseases.
Molecular biologist Stephen Nilsson-Møller, MSc, and colleagues at the department of clinical microbiology, Copenhagen University Hospital, developed and validated the test, known as the Dried Blood Spot (DBS), for HIV, HBV, and HCV.
The “test that can detect low viral loads for all three viruses from a single drop of blood, and can be done using existing hospital equipment,” Mr. Nilsson-Møller said in an interview. “Importantly, it does not require venipuncture, but can be done from a drop of dried blood from the finger.”
He highlighted the utility of the new test in more challenging settings. “This method is particularly useful in high-risk settings such as homeless shelters, drug rehabilitation centers, and prisons, where needles might be misused, and it can be difficult to convince people to have the more invasive test.”
“Also, in some places – such as in low- and middle-income settings – there is a distinct risk of ruining blood samples before analysis due to limited refrigeration for transit and storage,” he added. “[Standard] blood samples need to be analyzed within 6 hours when kept at room temperature, while dried blood spots can last for 9 months at room temperature and can be mailed to a laboratory with the right equipment to analyze it.”
Tiny amounts of virus detected
Mr. Nilsson-Møller was tasked with developing a test for use by the university’s department of infectious diseases to screen people in high-risk settings in the capital region of Copenhagen. The work forms part of a PhD project by Jonas Demant at the University of Copenhagen, for which he is screening for HIV, HBV, and HCV in drug rehabilitation centers, prisons, and homeless shelters.
The study is the first to use the Hologic Panther system (a nucleic acid amplification test) combining all three viruses, Mr. Nilsson-Møller pointed out. “A tiny amount of virus can be detected because it is a very sensitive platform using transcription-mediated amplification.”
“If it detects low amounts of virus, it will create many copies very quickly, creating a signal that tells us that the sample is positive,” he explained.
The researchers collected whole blood from a finger prick, dried it out on a protein saver card (filter paper), and cut out a 1.2-cm diameter dry blood spot which was then prepared for analysis.
Twenty blood samples with known amounts of HIV, HBV, and HCV were analyzed via the DBS method (60 in total) and the viruses were detected in all of the samples.
To validate the method, the researchers used plasma with a known viral load, and a series of dilutions were performed to determine the lower limit for positive detection of all three viruses.
“Untreated patients typically have above 1 million IU/mL of viral loads in their plasma, and we found that we can detect much lower levels,” said Mr. Nilsson-Møller. “Ideally, 40 mcL of blood is good, but less should be sufficient if the test is on untreated patients.”