*3.2. μBAR Platform*

Myers et al. have developed the Microfluidic Biomolecular Amplification Reader (μBAR) in an attempt to combine electronics, optics, microfluidics, and molecular biology. The μBAR is a battery-powered, portable instrument capable of isothermal amplification of multiple markers with the use disposable microfluidic assay cartridges. First, the sample (i.e., blood, sputum, or saliva) is loaded onto a disposable microfluidic cartridge, where the system uses a loop-mediated isothermal amplification (LAMP) technique. The cartridge is then inserted into the μBAR, where it will control assay temperature, illuminate the chip, and monitor real-time fluorescence signals from individual reaction chambers [47,48].

Previously, the LAMP assay was verified to detect HIV and malaria from blood samples and TB drug resistance from sputum samples. Myers et al. have also exhibited use of the LAMP assay on the μBAR platform in detecting the HIV integrase gene. The platform also has GPS and cellphone connectivity for healthcare delivery in remote locations and epidemiological surveillance. The chip contains six inlets, meaning multiple samples can be loaded simultaneously. In its current form, the μBAR requires more work to modify for HIVDR detection [48].

#### *3.3. Oxford Nanopore MinION (ONT) Sequencing*

The increase in using NGS technologies to detect HIVDR have been on the rise. It is noteworthy that most of available NGS platforms are not even close to the bedside POCT considering their prohibitive instrument and reagen<sup>t</sup> costs, demanding technical operation and complexity in data interpretation. One exception could be the MinION platform, developed by the Oxford Nanopore Technologies (https://nanoporetech.com/, accessed on 16 June 2022). MinION is thus far the only portable device that execute NGS on DNA or RNA templates with minimal requirement for additional instrumental and technical support.

Gonzalez et al. pioneered applying MinION sequencing to HIVDR analysis. HIV RNA was first extracted from plasma samples followed by PCR amplification. PCR products were then prepared for MinION library preparation and a sequencing library was generated to load into a flow cell. Good concordance was observed between the MinION consensus sequences and the Sanger sequencing outputs from the same patients, regarding both the sequence identity and HIVDR profiling [49]. While their findings support the usage of ONT in decentralized laboratories, the scarcity of supporting data from other labs warrants further investigation on the full potentials of MinION technologies in HIVDR POCT.

*The technologies listed in this section are but a snippet of potential and relevant assays. For example, techniques that use GeneXpert, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR), and High-Resolution Melting (HRM) have also been implemented in drug resistance* *detection for varying pathogens. Perhaps these methods, coupled with the rise in technological advancement, may inspire new HIVDR POCTs.*
