research in low-resource regions is feasible with microsampling

Scientists often find it challenging to collect specimen samples from study subjects in less developed countries for their research studies of malnutrition, infectious diseases, and other public health problems. One challenge is a lack of resources to keep the specimen samples stable during transport to a lab. For example, traditional wet blood samples collected in tubes must be kept frozen or chilled to maintain stability for accurate lab analysis.

Lack of access to electricity and refrigeration for storage and cold-chain shipping of liquid samples makes it challenging to keep them stable and viable for bioanalysis.

Field researchers collecting samples in low-resource regions also contend with limited budgets; another problem that limits their research studies in many parts of the world. Limited funding often prevents them from acquiring and deploying the necessary supplies, equipment, and large medical teams they require to conduct studies in remote, under-developed settings.

Fortunately, dried blood spot (DBS) sampling cards and volumetric absorptive microsampling devices are two dried matrix sampling solutions that help researchers overcome these challenges of field research. There are, of course, pros and cons to consider when using these dried matrix sampling solutions, so let's take a closer look at the specific advantages and disadvantages.

Dried Matrix Sampling for Low-Resource Regions

Generally speaking, dried matrix sampling entails using a finger-stick method to collect small blood drops onto a filter card or onto a microsampling device specially made for dried blood spot analysis. The finger-stick sampling method has several advantages when used in low-resource field settings.

Pros:

• Dried blood samples don't require refrigeration, which simplifies storage and transport logistics when cold chain isn't available.
• Finger-stick sampling is an easy method that doesn’t require trained staff, such as phlebotomists, to perform.
• The dried matrix approach enhances the stability of the samples by preserving the analytes, even in tropical environments.
• Some volumetric microsampling devices reliably collect a fixed-volume specimen sample that consistently provide good data the bioanalytical lab
• Dried specimen samples furnish robust data that correlates well with traditional venipuncture liquid samples

Cons:

• DBS cards have a high failure rate, especially when samples are collected outside a clinical setting.
• Standard DBS has the potential for sampling bias. The uneven filling of samples in the spotting areas on the card leads to blood hematocrit issues that negatively impact quantitative measurements.

Differences in Sample Handling & Shipping

With the finger-stick sample collection method, capillary blood samples are ready to be transported as soon as they are dry. They don’t require dry ice or cooling equipment. However, the drying method differs when using a DBS filter card compared to using a microsampling device like the Mitra^® device.

The DBS card, made of filter paper, must be left out to air-dry completely after blood sampling before it can be packaged for shipping. Not drying DBS cards thoroughly can cause them to contaminate other sampled cards contained in the same package. On the other hand, a Mitra microsampling device doesn't require the extra step of drying before shipment.

The Mitra devices come in a protective plastic cartridge and a sealable foil bag with a packet of drying desiccant inside. After collecting blood samples, Mitra users can close the devices in their cartridge and slip the cartridge case into the foil bag for immediate shipment. Thanks to the included desiccant, the samples dry within their protective bags during transit and are protected from contamination.

A Review of the Pros and Cons

Volumetric microsampling technologies, such as the Mitra device with the original, patented VAMS tips, eliminate the hematocrit bias of DBS cards, because they collect a fixed-volume blood sample. The samples collected using the VAMS technology have a lower sample rejection rate, which means that more high-quality samples contribute to the study data, without the need to return to the study population to repeat-sample them.

What may appear to be a disadvantage at the beginning of a study project is the price. Volumetric microsampling technologies can represent a higher cost than DBS cards. Research labs working in low-resource areas may not think they have the budget to cover the volumetric microsampling option, but once they account for the number of repeat-samples required with DBS cards, a cost-benefit analysis often shows that volumetric microsampling is more feasible. It is much more challenging to have to ask for more money partway through a project because it is necessary to repeat the sampling component in order to gather a sufficient number of useable samples.

For some researchers accustomed to processing and analyzing wet blood samples, finger-stick sampling deviates too much from their standard protocols. This has prevented the adoption of remote microsampling techniques on a broad scale among various labs. However, with the increasing need for remote technologies that can be reliably applied across a range of environments, more labs are starting to use microsampling, including the volumetric absorptive approach.