Monitoring treatment: at what cost?

Point of care testing for infectious diseases

Infectious diseases are caused by pathogenic microorganisms and can be transmitted between individuals and populations thus threatening the general public health and potentially the economy. Efficient diagnostic tools are needed to provide accurate and timely guidance for case identification, transmission disruption and appropriate treatment administration. Point of care (POC) tests provide actionable results near the patient and thereby serve as a personal "radar". In this review, we review clinical needs for POC testing for several major pathogens, including malaria parasites, human immunodeficiency virus (HIV), human papillomavirus (HPV), dengue, Ebola and Zika viruses and Mycobacterium tuberculosis (TB). We compare different molecular approaches, including pathogen nucleic acid and protein, circulating microRNA and antibodies, used in the POC tests. Finally, we review recent advances in novel POC technologies focusing on microfluidic and plasmonic-based approaches.

Cell manipulation in microfluidics

Recent advances in the lab-on-a-chip field in association with nano/microfluidics have been made for new applications and functionalities to the fields of molecular biology, genetic analysis and proteomics, enabling the expansion of the cell biology field. Specifically, microfluidics has provided promising tools for enhancing cell biological research, since it has the ability to precisely control the cellular environment, to easily mimic heterogeneous cellular environment by multiplexing, and to analyze sub-cellular information by high-contents screening assays at the single-cell level. Various cell manipulation techniques in microfluidics have been developed in accordance with specific objectives and applications. In this review, we examine the latest achievements of cell manipulation techniques in microfluidics by categorizing externally applied forces for manipulation: (i) optical, (ii) magnetic, (iii) electrical, (iv) mechanical and (v) other manipulations. We furthermore focus on history where the manipulation techniques originate and also discuss future perspectives with key examples where available.

Simultaneous counting of two subsets of leukocytes using fluorescent silica nanoparticles in a sheathless microchip flow cytometer

A portable flow cytometer has been recognized as an important tool for many clinical applications such as HIV/AIDS screening in developing countries and regions with limited medical facilities and resources. Conventional flow cytometers typically require multiple detectors for simultaneous identification of multiple subsets of immune cell. To minimize the number of detectors toward portable flow cytometry or to analyze multi-parametric cellular information with minimum number of detectors in conventional flow cytometers, we propose a versatile multiplexed cell-counting method using functional silica nanoparticles (SiNPs). FITC-doped SiNPs, which are 100 times brighter than the FITC molecules itself, were used as new intensity-based fluorescent dye complexes to simultaneously measure two subsets of leukocytes using a single detector. CD45(+)CD4(+) cells tagged with these FITC-doped SiNPs were 50 times brighter than CD45(+)CD4(-) cells tagged only with FITC. To make the overall system compact, a disposable microchip flow cytometer that does not require sheath flow was developed. Combining these dye-doped SiNPs based detection schemes and the sheathless microchip flow cytometer scheme, we successfully identified and counted two subsets of leukocytes simultaneously (R(2) = 0.876). These approaches can be the building blocks for a truly portable and disposable flow cytometer for various clinical cytometry applications.

Nano/Microfluidics for diagnosis of infectious diseases in developing countries

Nano/Microfluidic technologies are emerging as powerful enabling tools for diagnosis and monitoring of infectious diseases in both developed and developing countries. Miniaturized nano/microfluidic platforms that precisely manipulate small fluid volumes can be used to enable medical diagnosis in a more rapid and accurate manner. In particular, these nano/microfluidic diagnostic technologies are potentially applicable to global health applications, since they are disposable, inexpensive, portable, and easy-to-use for detection of infectious diseases. In this paper, we review recent advances in nano/microfluidic technologies for clinical point-of-care applications at resource-limited settings in developing countries.

Programmable nano-bio-chips: multifunctional clinical tools for use at the point-of-care

A new generation of programmable diagnostic devices is needed to take advantage of information generated from the study of genomics, proteomics, metabolomics and glycomics. This report describes the 'programmable nano-bio-chip' with potential to bridge the significant scientific, technology and clinical gaps through the creation of a diagnostic platform to measure the molecules of life. This approach, with results at the point-of-care, possesses capabilities for measuring such diverse analyte classes as cells, proteins, DNA and small molecules in the same compact device. Applications such as disease diagnosis and prognosis for areas including cancer, heart disease and HIV are described. New diagnostic panels are inserted as 'plug and play' elements into the modular platform with universal assay operating systems and standard read out sequences. The nano-bio-chip ensemble exhibits excellent analytical performance and cost-effectiveness with extensive validation versus standard reference methods (R(2) = 0.95-0.99). This report describes the construction and use of two major classes of nano-bio-chip designs that serve as cellular and chemical processing units, and provides perspective on future growth in this newly emerging field of programmable nano-bio-chip sensor systems.

Current developments in salivary diagnostics

Salivary diagnostics is an emerging field that has progressed through several important developments in the past decade, including the publication of the human salivary proteome and the infusion of federal funds to integrate nanotechnologies and microfluidic engineering concepts into developing compact point-of-care devices for rapid analysis of this secretion. In this article, we discuss some of these developments and their relevance to the prognosis, diagnosis and management of periodontitis, as an oral target, and cardiovascular disease, as a systemic example for the potential of these biodiagnostics. Our findings suggest that several biomarkers are associated with distinct biological stages of these diseases and demonstrate promise as practical biomarkers in identifying and managing periodontal disease, and acute myocardial infarction. The majority of these studies have progressed through biomarker discovery, with the identified molecules requiring more robust clinical studies to enable substantive validation for disease diagnosis. It is predicted that with continued advances in this field the use of a combination of biomarkers in multiplex panels is likely to yield accurate screening tools for these diagnoses in the near future.

Use of saliva-based nano-biochip tests for acute myocardial infarction at the point of care: a feasibility study

BACKGROUND

For adults with chest pain, the electrocardiogram (ECG) and measures of serum biomarkers are used to screen and diagnose myocardial necrosis. These measurements require time that can delay therapy and affect prognosis. Our objective was to investigate the feasibility and utility of saliva as an alternative diagnostic fluid for identifying biomarkers of acute myocardial infarction (AMI).

METHODS

We used Luminex and lab-on-a-chip methods to assay 21 proteins in serum and unstimulated whole saliva procured from 41 AMI patients within 48 h of chest pain onset and from 43 apparently healthy controls. Data were analyzed by use of logistic regression and area under curve (AUC) for ROC analysis to evaluate the diagnostic utility of each biomarker, or combinations of biomarkers, in screening for AMI.

RESULTS

Both established and novel cardiac biomarkers demonstrated significant differences in concentrations between patients with AMI and controls without AMI. The saliva-based biomarker panel of C-reactive protein, myoglobin, and myeloperoxidase exhibited significant diagnostic capability (AUC = 0.85, P < 0.0001) and in conjunction with ECG yielded strong screening capacity for AMI (AUC = 0.96) comparable to that of the panel (brain natriuretic peptide, troponin-I, creatine kinase-MB, myoglobin; AUC = 0.98) and far exceeded the screening capacity of ECG alone (AUC approximately 0.6). En route to translating these findings to clinical practice, we adapted these unstimulated whole saliva tests to a novel lab-on-a-chip platform for proof-of-principle screens for AMI.

CONCLUSIONS

Complementary to ECG, saliva-based tests within lab-on-a-chip systems may provide a convenient and rapid screening method for cardiac events in prehospital stages for AMI patients.

Integration of semiconductor quantum dots into nano-bio-chip systems for enumeration of CD4+ T cell counts at the point-of-need

Recent humanitarian efforts have led to the widespread release of antiretroviral drugs for the treatment of the more than 33 million HIV afflicted people living in resource-scarce settings. Here, the enumeration of CD4+ T lymphocytes is required to establish the level at which the immune system has been compromised. The gold standard method used in developed countries, based on flow cytometry, though widely accepted and accurate, is precluded from widespread use in resource-scarce settings due to its high expense, high technical requirements, difficulty in operation-maintenance and the lack of portability for these sophisticated laboratory-confined systems. As part of continuing efforts to develop practical diagnostic instrumentation, the integration of semiconductor nanocrystals (quantum dots, QDs) into a portable microfluidic-based lymphocyte capture and detection device is completed. This integrated system is capable of isolating and counting selected lymphocyte sub-populations (CD3+CD4+) from whole blood samples. By combining the unique optical properties of the QDs with the sample handling capabilities and cost effectiveness of novel microfluidic systems, a practical, portable lymphocyte measurement modality that correlates nicely with flow cytometry (R2 = 0.97) has been developed. This QD-based system reduces the optical requirements significantly relative to molecular fluorophores and the mini-CD4 counting device is projected to be suitable for use in both point-of-need and resource-scarce settings.

Pharmacy refill adherence compared with CD4 count changes for monitoring HIV-infected adults on antiretroviral therapy

BACKGROUND

World Health Organization (WHO) guidelines for monitoring HIV-infected individuals taking combination antiretroviral therapy (cART) in resource-limited settings recommend using CD4(+) T cell (CD4) count changes to monitor treatment effectiveness. In practice, however, falling CD4 counts are a consequence, rather than a cause, of virologic failure. Adherence lapses precede virologic failure and, unlike CD4 counts, data on adherence are immediately available to all clinics dispensing cART. However, the accuracy of adherence assessments for predicting future or detecting current virologic failure has not been determined. The goal of this study therefore was to determine the accuracy of adherence assessments for predicting and detecting virologic failure and to compare the accuracy of adherence-based monitoring approaches with approaches monitoring CD4 count changes.

METHODOLOGY AND FINDINGS

We conducted an observational cohort study among 1,982 of 4,984 (40%) HIV-infected adults initiating non-nucleoside reverse transcriptase inhibitor-based cART in the Aid for AIDS Disease Management Program, which serves nine countries in southern Africa. Pharmacy refill adherence was calculated as the number of months of cART claims submitted divided by the number of complete months between cART initiation and the last refill prior to the endpoint of interest, expressed as a percentage. The main outcome measure was virologic failure defined as a viral load > 1,000 copies/ml (1) at an initial assessment either 6 or 12 mo after cART initiation and (2) after a previous undetectable (i.e., < 400 copies/ml) viral load (breakthrough viremia). Adherence levels outperformed CD4 count changes when used to detect current virologic failure in the first year after cART initiation (area under the receiver operating characteristic [ROC] curves [AUC] were 0.79 and 0.68 [difference = 0.11; 95% CI 0.06 to 0.16; chi(2) = 20.1] respectively at 6 mo, and 0.85 and 0.75 [difference = 0.10; 95% CI 0.05 to 0.14; chi(2) = 20.2] respectively at 12 mo; p < 0.001 for both comparisons). When used to detect current breakthrough viremia, adherence and CD4 counts were equally accurate (AUCs of 0.68 versus 0.67, respectively [difference = 0.01; 95% CI -0.06 to 0.07]; chi(2) = 0.1, p > 0.5). In addition, adherence levels assessed 3 mo prior to viral load assessments were as accurate for virologic failure occurring approximately 3 mo later as were CD4 count changes calculated from cART initiation to the actual time of the viral load assessments, indicating the potential utility of adherence assessments for predicting future, rather than simply detecting current, virologic failure. Moreover, combinations of CD4 count and adherence data appeared useful in identifying patients at very low risk of virologic failure.

CONCLUSIONS

Pharmacy refill adherence assessments were as accurate as CD4 counts for detecting current virologic failure in this cohort of patients on cART and have the potential to predict virologic failure before it occurs. Approaches to cART scale-up in resource-limited settings should include an adherence-based monitoring approach.

Ultra wide-field lens-free monitoring of cells on-chip

We experimentally and theoretically demonstrate the proof-of-principle of a new lens-free cell monitoring platform that involves using an opto-electronic sensor array to record the shadow image of cells onto the sensor plane. This technology can monitor/count cells over a field-of-view that is more than two orders of magnitude larger than that of a conventional light microscope. Furthermore, it does not require any mechanical scanning or optical elements, such as microscope objectives or lenses. We also show that this optical approach can conveniently be combined with microfluidic channels, enabling parallel on-chip monitoring of various different cell types, e.g., blood cells, NIH-3T3 fibroblasts, murine embryonic stem cells, AML-12 hepatocytes. An important application of this approach could be a miniaturized point-of-care technology to obtain CD4 T lymphocyte counts of HIV infected patients in resource limited settings.

Microchip-based enumeration of human white blood cells

The advent of flow cytometry has considerably changed the ways in which medical testing is conducted. However, the cost of flow cytometers, their large size, and their maintenance needs make them scarce in resource-poor settings and available almost only in clinical pathology laboratories in developed countries. Because cell enumeration is a basic and crucial support of diagnosis, prognosis, and treatment, an alternative cell-counting method that would potentially be cost-effective, portable, and suitable for use in resource-poor settings is warranted. We describe here a protocol for conducting cell-counting experiments in a simple microfluidic structure. This protocol describes how to build a simple microfluidic cell and perform a total white blood cell (WBC) count through capture and immunolabeling of the WBCs with an anti-CD45 antibody.

A new model to monitor the virological efficacy of antiretroviral treatment in resource-poor countries

Monitoring the efficacy of antiretroviral treatment in developing countries is difficult because these countries have few laboratory facilities to test viral load and drug resistance. Those that exist are faced with a shortage of trained staff, unreliable electricity supply, and costly reagents. Not only that, but most HIV patients in resource-poor countries do not have access to such testing. We propose a new model for monitoring antiretroviral treatment in resource-limited settings that uses patients' clinical and treatment history, adherence to treatment, and laboratory indices such as haemoglobin level and total lymphocyte count to identify virological treatment failure, and offers patients future treatment options. We believe that this model can make an accurate diagnosis of treatment failure in most patients. However, operational research is needed to assess whether this strategy works in practice.