At-Home Answers in Infectious Disease

As patients seek more knowledge and control of their health, the popularity of at-home diagnostic testing is rising. A 2023 survey of 200 supply chain professionals revealed that 97 percent had seen an increase in the demand for at-home tests since 2021¹—and, although COVID-19 testing may have introduced consumers to the idea of performing their own diagnostics, people’s interest in at-home testing ranges from fertility to food allergies. The market for these tests, which was valued at just under $17 billion in 2021, is expected to almost triple by 2031,² largely driven—especially in the United States—by demand from insurance providers who want to offer their clients privacy and convenience.¹ But what’s new in the world of at-home testing—and what does it mean for the lab?

Respiratory pathogen testing

Though home testing for infectious disease has been available for decades,³ the onset of the COVID-19 pandemic significantly increased public familiarity and comfort with self-testing. With SARS-CoV-2 still a global threat and rapid antigen tests demonstrating limited diagnostic sensitivity,⁴ research into more accurate at-home testing is a priority.

To bring molecular testing into the home environment, a new study introduces a paper-based nucleic acid detection device for easy, rapid diagnosis of COVID-19 and influenza via reverse transcription loop-mediated isothermal amplification (RT-LAMP).⁵ The device can simultaneously detect up to eight different sequences in a single nasal swab sample, meaning that it can be adapted for a wide range of pathogens, and delivers results within 30 minutes. To further improve the accuracy and reliability of at-home RT-LAMP testing, another group of researchers developed a duplex assay that incorporates internal amplification controls without increasing assay complexity.⁶ The test yields a three-line readout (flow control, amplification control, and the test line in the case of a positive saliva sample) after 30 minutes and, when applied to 30 saliva samples, demonstrated 95 percent sensitivity, 100 percent specificity, and 96 percent accuracy for SARS-CoV-2 detection.

Additional research into at-home respiratory pathogen testing has focused on new approaches to increasing accuracy and sensitivity. To achieve this, one research group developed a device that includes a microfluidic chip for sample handling, a heater, a Cas13-based sensor for RNA detection, and a connector that transmits the data to a smartphone for analysis, delivering PCR-equivalent sensitivity in less than half an hour.⁷ Although developed for SARS-CoV-2, the platform can be adapted to detect other viral pathogens. In response to rising concerns regarding respiratory and zoonotic infections more generally, another group developed a CRISPR-Cas12 system that simultaneously detects five pathogens, some of which have zoonotic potential—SARS-CoV-2, Mycoplasma felis, Chlamydia felis, feline calicivirus, and feline herpesvirus—with over 94 percent sensitivity and 100 percent specificity.⁸ The single-use device requires no special skills or expertise and delivers results in under 40 minutes; its creators now hope to develop a reusable or recyclable version and to expand testing to additional pathogens such as newer SARS-CoV-2 variants. The current focus on nucleic acid detection doesn’t mean that antigen testing has fallen by the wayside, though; a research group from Beijing recently developed a test that uses a photonic crystal microarray to detect SARS-CoV-2 nucleocapsid proteins present at levels as low as 0.03 pg/mL⁹—orders of magnitude better than some of the most sensitive rapid antigen tests currently in use.¹⁰

Sexually transmitted infections

Although COVID-19 popularized at-home infectious disease testing, some of the earliest such tests were developed for sexually transmitted infections (STIs). Mail-in HIV test kits have been available since the 1990s, but the first fully at-home, over-the-counter HIV test was approved in 2012;¹¹ it remains the only HIV self-test approved in the United States, although others are available elsewhere.¹² Whether testing involves a self-collected mail-in sample or a fully independent result, however, adherence remains a challenge in many situations. Recent research has focused on expanding acceptance and uptake globally, finding that self-directed options led to an increase in people’s willingness to test in the United States,¹³ Kazakhstan,¹⁴ Japan,¹⁵ Spain,¹⁶ and five African countries.¹⁷ Social motivation further increases willingness to test; peer education and distribution are broadly linked to increased testing rates, especially in marginalized populations.^18,19 In China, researchers are now using machine learning to identify key peer influences for at-home HIV test distribution,²⁰ whereas in the UK and Japan, stocking digital vending machines with at-home test kits for purchase shows promise for increasing both access and willingness to test.¹⁵

But HIV is no longer the only STI for which at-home testing is available. On November 15, 2023, the U.S. Food and Drug Administration granted the first De Novo classification request for a chlamydia and gonorrhea test that incorporates at-home sample collection.²¹ (Other STI testing kits are available, but lack FDA approval for use with self-collected samples.) Research indicates that self-collecting samples may increase people’s acceptance of and comfort with STI testing in a range of settings and populations,^22,23 but barriers such as fear of the procedure, anxiety over results, and socioeconomic factors still affect test uptake.²⁴

Although mpox is not exclusively transmitted via sexual contact, most cases are acquired through close or intimate contact, so it is often considered an STI or handled in a similar manner.²⁵ Given the social stigma often associated with STIs and the 2022–2023 mpox outbreak that constituted a public health emergency of international concern, research has focused on rapid, at-home mpox virus testing. The result? A portable, 3D-printed device that uses recombinase polymerase amplification and a CRISPR-Cas12a system to detect mpox RNA in samples of lesion fluid. When tested on 104 mock clinical samples, the device delivered clinical sensitivity of 91.7 percent for the viral F3L gene and 95.8 percent for the B6R gene, along with 100 percent specificity.²⁶ The device can be adapted to detect other pathogens and may offer promise in both home and point-of-care settings.

The future of at-home diagnostics

Research is ongoing into better options for at-home testing. New devices have been developed to evaluate HIV viral load,²⁷ improve home and point-of-care blood sample collection,²⁸ and even replace equipment-heavy traditional protocols with simple, affordable capillaric chips that can be 3D-printed in half an hour for a variety of single-analyte tests.²⁹ These advances are not limited to infectious disease diagnosis; new options for glucose testing,³⁰ HbA1c monitoring,³¹ and even kidney function self-testing³² are under investigation. As consumer interest in privacy, convenience, and autonomy continues to grow, self-collected samples are likely to become an increasing presence in the clinical lab and may necessitate new protocols for sample management, quality control, and patient education.

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