Simple paper-based test for measuring blood hemoglobin concentration in resource-limited settings

In-situ synthesis of ionic liquid-based-carbon quantum dots as fluorescence probe for hemoglobin detection

Carbon quantum dots (CQDs) have emerged as a potential fluorescent probe in bio/analytical chemistry in the present decade. The optical characteristics of CQDs may be tuned by their functional groups, which can also be used to selectively produce stable bonds with target molecules. Along with them, ionic liquids (ILs) are now demonstrating their important relevance in the field of pharmaceuticals for the creation of potent therapeutics. In the article, we have discussed the use of high fluorescent ILs-decorated-CQDs (CQDs-IM@OTf) as a straightforward and quick-acting fluorescence probe for sensitive and precise hemoglobin (Hb) determination with minimum detectability of 6.7 nM. The proposed mechanism behind this involves static mode of quenching which leads to the formation of a ground state complex [CQDs-IM@OTf-Hb complex] between the Hb protein and the drug. Despite the fact that Hb can quench the fluorescence of CQDs due to the inner filter effect (IFE) of the protein, which effects both the excitation and emission spectra of the CQDs, the addition of H₂O₂ improved the sensitivity of Hb detection. The present assay predicated on Hb interaction with H₂O₂, which produces reactive oxygen species such as hydroxyl (OH^.) and superoxide (O₂^.-) radicals under heme degradation and/or iron release from Hb. The subsequent reaction of hydroxyl radicals with CQDs, which acts as a strong oxidising agent, causes a high fluorescence quenching. The designed fluorescence probe was used to measure Hb in the concentration range of 3-90 nM with a precise detection limit of 0.33 nM. The quantification of hemoglobin (Hb) in diluted human blood samples is done using this observation.

On the Application of Microfluidic-Based Technologies in Forensics: A Review

Microfluidic technology is a powerful tool to enable the rapid, accurate, and on-site analysis of forensically relevant evidence on a crime scene. This review paper provides a summary on the application of this technology in various forensic investigation fields spanning from forensic serology and human identification to discriminating and analyzing diverse classes of drugs and explosives. Each aspect is further explained by providing a short summary on general forensic workflow and investigations for body fluid identification as well as through the analysis of drugs and explosives. Microfluidic technology, including fabrication methodologies, materials, and working modules, are touched upon. Finally, the current shortcomings on the implementation of the microfluidic technology in the forensic field are discussed along with the future perspectives.

Vessel Pulse Amplitude Mapping in Eyes With Central and Hemi Retinal Venous Occlusion

Purpose

The purpose of this study was to describe vessel pulse amplitude characteristics in eyes with central retinal vein occlusion (CRVO), hemiretinal vein occlusion (HVO), normal eyes (N1 N1), and the unaffected contralateral eyes of CRVO and HVO eyes (N1 CRVO and N1 HVO), as well as the unaffected hemivessels of HVO eyes (N2 HVO).

Methods

Ophthalmodynamometry estimates of blood column pulse amplitudes with modified photoplethysmography were timed against cardiac cycles. Harmonic analysis was performed on the vessel reflectance within 0.25 to 1 mm from the disc center to construct pulse amplitude maps. Linear mixed modeling was used to examine variable effects upon the log harmonic pulse amplitude.

Results

One hundred seven eyes were examined. Normal eyes had the highest mean venous pulse amplitude (2.08 ± 0.48 log u). CRVO had the lowest (0.99 ± 0.45 log u, P < 0.0001), followed by HVO (1.23 ± 0.46 log u, P = 0.0002) and N2 HVO (1.30 ± 0.59 log u, P = 0.0005). N1 CRVO (1.76 ± 0.34 log u, P = 0.52) and N1 HVO (1.33 ± 0.37 log u, P = 0.0101) had no significantly different mean amplitudes compared to N1 N1. Arterial amplitudes were lower than venous (P < 0.01) and reduced with venous occlusion (P < 0.01). Pulse amplitude versus amplitude over distance decreased along the N1 N1 vessels, with increasing slopes observed with CRVO (P < 0.01).

Conclusions

Pulse amplitude reduction and attenuation characteristics of arteries and veins in venous occlusion can be measured and are consistent with reduced vessel wall compliance and pulse wave transmission.

Translational Relevance

Retinal vascular pulse amplitudes can be measured, revealing occlusion induced changes, suggesting a role in evaluating the severity and progression of venous occlusion.

Translating diagnostics and drug delivery technologies to low-resource settings

Diagnostics and drug delivery technologies engineered for low-resource settings aim to meet their technical design specifications using strategies that are compatible with limited equipment, infrastructure, and operator training. Despite many preclinical successes, very few of these devices have been translated to the clinic. Here, we identify factors that contribute to the clinical success of diagnostics and drug delivery systems for low-resource settings, including the need to engage key stakeholders at an early stage, and provide recommendations for the clinical translation of future medical technologies.

PlyAB Nanopores Detect Single Amino Acid Differences in Folded Haemoglobin from Blood

The real‐time identification of protein biomarkers is crucial for the development of point‐of‐care and portable devices. Here, we use a PlyAB biological nanopore to detect haemoglobin (Hb) variants. Adult haemoglobin (HbA) and sickle cell anaemia haemoglobin (HbS), which differ by just one amino acid, were distinguished in a mixture with more than 97 % accuracy based on individual blockades. Foetal Hb, which shows a larger sequence variation, was distinguished with near 100 % accuracy. Continuum and Brownian dynamics simulations revealed that Hb occupies two energy minima, one near the inner constriction and one at the trans entry of the nanopore. Thermal fluctuations, the charge of the protein, and the external bias influence the dynamics of Hb within the nanopore, which in turn generates the unique ionic current signal in the Hb variants. Finally, Hb was counted from blood samples, demonstrating that direct discrimination and quantification of Hb from blood using nanopores, is feasible.

Smartphone-Integrated Label-Free Rapid Screening of Anemia from the Pattern Formed by One Drop of Blood on a Wet Paper Strip

Screening of anemic patients poses demanding challenges in extreme point-of-care settings where the gold standard diagnostic technologies are not pragmatic and the alternative point-of-care technologies suffer from compromised accuracy, prohibitive cost, process complexity, or reagent stability issues. As a disruption to this paradigm, here, we report the development of a smartphone-based sensor for rapid screening of anemic patients by exploiting the patterns formed by a spreading drop of blood on a wet paper strip wherein blood attempts to displace a more viscous fluid, on the porous matrix of a paper, leading to "finger-like" projections at the interface. We analyze the topological features of the pattern via smartphone-enabled image analytics and map the same with the relative occupancy of the red blood cells in the blood sample, allowing for label-free screening and classification of blood samples corresponding to moderate to severe anemic conditions. The accuracy of detection is verified by comparing with gold standard reports of hematology analyzer, showing a strong correlation coefficient (R²) of 0.975. This technique is likely to provide a crucial decision-making tool that obviates delicate reagents and skilled technicians for supreme functionality in resource-limited settings.

Point-of-care haemoglobin testing in African hospitals: a neglected essential diagnostic test

Owing to the rapid turnaround time in the assessment of haemoglobin level by point-of-care tests (POC Hb), these have grown in popularity and scope in large parts of the world. However, whilst POC testing for malaria and HIV remains has been integrated into patient management in Africa, the use of POC haemoglobin testing remains neglected by health services. The main users of transfusions (paediatric, maternity and trauma services) present largely as emergencies. Ward-based POC Hb could result in more rapid and accurate diagnosis of anaemia, contributing to saving of lives and at the same time reduce unnecessary transfusions which deplete the limited supplies of donated blood in Africa. Severe anaemia requiring transfusion is a major cause of paediatric admission in Africa. At a dissemination meeting to discuss the results of a large phase III paediatric transfusion trial and steps to implementation of the findings participants strongly recommended that one of the most pressing actions required was to prioritise the use of POC haemoglobin testing. This would facilitate implementation of the new transfusion algorithm, developed at the meeting, which refines patient management including blood transfusions. We present the rationale for the strongly recommended prioritisation of POC Hb, using paediatric transfusion as an exemplar.

Smartphone-Based Fully Automated Optofluidic Device with Laser Irradiation-Induced Image Whitening

Herein, we have developed a fully automated optofluidic device to execute enzyme-linked immunosorbent assay (ELISA) using an active 96-well hybrid lab-on-a-chip (LOC) device. To automate the solution loading into the reaction zone of the device and the post-assayed signal analysis, laser irradiation-induced image whitening was utilized with a smartphone-based optical platform. Two optical phenomena were utilized in our platform to detect the liquid in the reaction chamber using a smartphone. First, by Fresnel's equation, the refraction difference between air and water resulted in the intensity change of the reflected light from the reaction chamber. Therefore, when the liquid was entering into the reaction chamber, the intensity of the reflected light was changed. Second, when the light intensity increases, the smartphone-captured image whitens out due to saturation, even when the red color light was incident. Therefore, by measuring the RGB value of the smartphone image, the intensity changes by the liquid movement in the reaction chamber were successfully monitored. Our platform showed a low detection limit of 7.81 pg/mL for the detection of the NT-proBNP human cardiac biomarker with almost a half standard deviation, compared to the manually operated LOC-based ELISA. As a fully automated LOC adopting a conventional 96-well ELISA platform, we thus concluded that the developed platform can be widely applied for point-of-care clinical tests.

Noninvasive Hemoglobin Level Prediction in a Mobile Phone Environment: State of the Art Review and Recommendations

BACKGROUND

There is worldwide demand for an affordable hemoglobin measurement solution, which is a particularly urgent need in developing countries. The smartphone, which is the most penetrated device in both rich and resource-constrained areas, would be a suitable choice to build this solution. Consideration of a smartphone-based hemoglobin measurement tool is compelling because of the possibilities for an affordable, portable, and reliable point-of-care tool by leveraging the camera capacity, computing power, and lighting sources of the smartphone. However, several smartphone-based hemoglobin measurement techniques have encountered significant challenges with respect to data collection methods, sensor selection, signal analysis processes, and machine-learning algorithms. Therefore, a comprehensive analysis of invasive, minimally invasive, and noninvasive methods is required to recommend a hemoglobin measurement process using a smartphone device.

OBJECTIVE

In this study, we analyzed existing invasive, minimally invasive, and noninvasive approaches for blood hemoglobin level measurement with the goal of recommending data collection techniques, signal extraction processes, feature calculation strategies, theoretical foundation, and machine-learning algorithms for developing a noninvasive hemoglobin level estimation point-of-care tool using a smartphone.

METHODS

We explored research papers related to invasive, minimally invasive, and noninvasive hemoglobin level measurement processes. We investigated the challenges and opportunities of each technique. We compared the variation in data collection sites, biosignal processing techniques, theoretical foundations, photoplethysmogram (PPG) signal and features extraction process, machine-learning algorithms, and prediction models to calculate hemoglobin levels. This analysis was then used to recommend realistic approaches to build a smartphone-based point-of-care tool for hemoglobin measurement in a noninvasive manner.

RESULTS

The fingertip area is one of the best data collection sites from the body, followed by the lower eye conjunctival area. Near-infrared (NIR) light-emitting diode (LED) light with wavelengths of 850 nm, 940 nm, and 1070 nm were identified as potential light sources to receive a hemoglobin response from living tissue. PPG signals from fingertip videos, captured under various light sources, can provide critical physiological clues. The features of PPG signals captured under 1070 nm and 850 nm NIR LED are considered to be the best signal combinations following a dual-wavelength theoretical foundation. For error metrics presentation, we recommend the mean absolute percentage error, mean squared error, correlation coefficient, and Bland-Altman plot.

CONCLUSIONS

We addressed the challenges of developing an affordable, portable, and reliable point-of-care tool for hemoglobin measurement using a smartphone. Leveraging the smartphone's camera capacity, computing power, and lighting sources, we define specific recommendations for practical point-of-care solution development. We further provide recommendations to resolve several long-standing research questions, including how to capture a signal using a smartphone camera, select the best body site for signal collection, and overcome noise issues in the smartphone-captured signal. We also describe the process of extracting a signal's features after capturing the signal based on fundamental theory. The list of machine-learning algorithms provided will be useful for processing PPG features. These recommendations should be valuable for future investigators seeking to build a reliable and affordable hemoglobin prediction model using a smartphone.

Smartphone-Enabled Paper-Based Hemoglobin Sensor for Extreme Point-of-Care Diagnostics

We report a simple, affordable (∼0.02 US $/test), rapid (within 5 min), and quantitative paper-based sensor integrated with smartphone application for on-spot detection of hemoglobin (Hgb) concentration using approximately 10 μL of finger-pricked blood. Quantitative analytical colorimetry is achieved via an Android-based application (Sens-Hb), integrating key operational steps of image acquisition, real-time analysis, and result dissemination. Further, feedback from the machine learning algorithm for adaptation of calibration data offers consistent dynamic improvement for precise predictions of the test results. Our study reveals a successful deployment of the extreme point-of-care test in rural settings where no infrastructural facilities for diagnostics are available. The Hgb test device is validated both in the controlled laboratory environment (n = 200) and on the field experiments (n = 142) executed in four different Indian villages. Validation results are well correlated with the pathological gold standard results (r = 0.9583) with high sensitivity and specificity for the healthy (n = 136) (>11 g/dL) (specificity: 97.2%), mildly anemic (n = 55) (<11 g/dL) (sensitivity: 87.5%, specificity: 100%), and severely anemic (n = 9) (<7 g/dL) (sensitivity: 100%, specificity: 100%) samples. Results from field trials reveal that only below 5% cases of the results are interpreted erroneously by classifying mildly anemic patients as healthy ones. On-field deployment has unveiled the test kit to be extremely user friendly that can be handled by minimally trained frontline workers for catering the needs of the underserved communities.

Point-of-care testing of plasma free hemoglobin and hematocrit for mechanical circulatory support

Hematological analysis is essential for patients who are supported by a mechanical circulatory support (MCS). The laboratory methods used to analyze blood components are conventional and accurate, but they require a mandatory turn-around-time for laboratory results, and because of toxic substances, can also be hazardous to analysis workers. Here, a simple and rapid point-of-care device is developed for the measurement of plasma free hemoglobin (PFHb) and hematocrit (Hct), based on colorimetry. The device consists of camera module, minimized centrifuge system, and the custom software that includes the motor control algorithm for the centrifuge system, and the image processing algorithm for measuring the color components of blood from the images. We show that our device measured PFHb with a detection limit of 0.75 mg/dL in the range of (0–100) mg/dL, and Hct with a detection limit of 2.14% in the range of (20–50)%. Our device had a high correlation with the measurement method generally used in clinical laboratories (PFHb R = 0.999, Hct R = 0.739), and the quantitative analysis resulted in precision of 1.44 mg/dL for PFHb value of 14.5 mg/dL, 1.36 mg/dL for PFHb value of 53 mg/dL, and 1.24% for Hct 30%. Also, the device can be measured without any pre-processing when compared to the clinical laboratory method, so results can be obtained within 5 min (about an 1 h for the clinical laboratory method). Therefore, we conclude that the device can be used for point-of-care measurement of PFHb and Hct for MCS.

Can phytoplankton blooming be harmful to benthic organisms? The toxic influence of Anabaena sp. and Chlorella sp. on Chironomus riparius larvae

Cyanobacteria and microalgae are abundant biota groups in eutrophic freshwater ecosystems, serving as a food source for many aquatic organisms, including the larvae of non-biting midges (Chironomidae). Many species of cyanobacteria are toxin producers, which can act as stressors to other organisms. The present study aimed to analyze and compare the effects of dietary exposure to the common toxic cyanobacteria Anabaena sp. and non-toxic microalgae Chlorella sp. in Chironomus riparius larvae. Microcystin was detected and quantified in the methanolic extract of Anabaena sp. using the HPLC-DAD technique, and it was identified as microcystin-LR. Both Anabaena sp. and Chlorella sp. were suitable food sources to enable the survival of C. riparius larvae in laboratory conditions, causing negligible mortality and significant differences in the larval mass (ANOVA and Post hoc LSD test; p < 0.05) and hemoglobin concentration (Student's t-test; p < 0.05). Oxidative stress parameters such as advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), catalase (CAT) and superoxide dismutase (SOD) activity, and DNA damage, were also investigated. One-way ANOVA, followed by the Post hoc LSD test, showed a significant increase in AOPP and CAT for the group of larvae fed with Chlorella sp. The same test showed moderate DNA damage in both groups of larvae, with greater damage in the group fed with Anabaena sp. Thus, Chlorella sp. and microcystin-LR producing Anabaena sp. are food sources that did not result in any drastic acute effect on the population level of C. riparius larvae. However, sub-individual-level endpoints revealed significant effects of the treatments, since they caused oxidative stress and DNA damage that may pose a danger to successive generations of test organisms.

Methods and analyzers for hemoglobin measurement in clinical laboratories and field settings

This paper describes and compares methods and analyzers used to measure hemoglobin (Hb) in clinical laboratories and field settings. We conducted a literature review for methods used to measure Hb in clinical laboratories and field settings. We described methods to measure Hb and factors influencing results. Automated hematology analyzer (AHA) was reference for all Hb comparisons using evaluation criteria of ±7% set by College of American Pathologists (CAP) and Clinical Laboratory Improvement Amendments (CLIA). Capillary fingerprick blood usually produces higher Hb concentrations compared with venous blood. Individual drops produced lower concentrations than pooled capillary blood. Compared with the AHA: (1) overall cyanmethemoglobin (1.0-8.0  g/L), WHO Colour Scale (0.5-10.0  g/L), paper-based devices (5.0-7.0  g/L), HemoCue® Hb-201 (1.0-16.0  g/L) and Hb-301 (0.5-6.0  g/L), and Masimo Pronto® (0.3-14.0  g/L) overestimated concentrations; (2) Masimo Radical®-7 both under- and overestimated concentrations (0.3-104.0  g/L); and (3) other methods underestimated concentrations (2.0-16.0  g/L). Most mean concentration comparisons varied less than ±7% of the reference. Hb measurements are influenced by several analytical factors. With few exceptions, mean concentration bias was within ±7%, suggesting acceptable performance. Appropriate, high-quality methods in all settings are necessary to ensure the accuracy of Hb measurements.This paper describes and compares methods and analyzers used to measure hemoglobin (Hb) in clinical laboratories and field settings. With few exceptions, mean concentration bias was within ±7%, suggesting acceptable performance. Appropriate, high-quality methods in all settings are necessary to ensure the accuracy of Hb measurements.

From Point-of-Care Testing to eHealth Diagnostic Devices (eDiagnostics)

Point-of-care devices were originally designed to allow medical testing at or near the point of care by health-care professionals. Some point-of-care devices allow medical self-testing at home but cannot fully cover the growing diagnostic needs of eHealth systems that are under development in many countries. A number of easy-to-use, network-connected diagnostic devices for self-testing are needed to allow remote monitoring of patients' health. This Outlook highlights the essential characteristics of diagnostic devices for eHealth settings and indicates point-of-care technologies that may lead to the development of new devices. It also describes the most representative examples of simple-to-use, point-of-care devices that have been used for analysis of untreated biological samples.

Screening of nutritional and genetic anemias using elastic light scattering

Anemia affects more than ¼ of the world's population, mostly concentrated in low-resource areas, and carries serious health risks. Yet current screening methods are inadequate due to their inability to separate iron deficiency anemia (IDA) from genetic anemias such as thalassemia trait (TT), thus preventing targeted supplementation of oral iron. Here we present an accurate approach to diagnose anemia and anemia type using measures of pediatric red cell morphology determined through machine learning applied to optical light scattering measurements. A partial least squares model shows that our system can accurately extract mean cell volume, red cell size heterogeneity, and mean cell hemoglobin concentration with high accuracy. These clinical parameters (or the raw data itself) can be submitted to machine learning algorithms such as quadratic discriminants or support vector machines to classify a patient into healthy, IDA, or TT. A clinical trial conducted on 268 Chinese children, of which 49 had IDA and 24 had TT, shows >98% sensitivity and specificity for diagnosing anemia, with 81% sensitivity and 86% specificity for discriminating IDA and TT. The majority of the misdiagnoses are IDA patients with particularly severe anemia, possibly requiring hospital care. Therefore, in a screening paradigm where anyone testing positive for TT is sent to the hospital for gold-standard diagnosis and care, we maximize patient benefit while minimizing use of scarce resources.

A modular, open-source, slide-scanning microscope for diagnostic applications in resource-constrained settings

In this paper we report the development of a cost-effective, modular, open source, and fully automated slide-scanning microscope, composed entirely of easily available off-the-shelf parts, and capable of bright field and fluorescence modes. The automated X-Y stage is composed of two low-cost micrometer stages coupled to stepper motors operated in open-loop mode. The microscope is composed of a low-cost CMOS sensor and low-cost board lenses placed in a 4f configuration. The system has approximately 1 micron resolution, limited by the f/# of available board lenses. The microscope is compact, measuring just 25×25×30 cm, and has an absolute positioning accuracy of ±1 μm in the X and Y directions. A Z-stage enables autofocusing and imaging over large fields of view even on non-planar samples, and custom software enables automatic determination of sample boundaries and image mosaicking. We demonstrate the utility of our device through imaging of fluorescent- and transmission-dye stained blood and fecal smears containing human and animal parasites, as well as several prepared tissue samples. These results demonstrate image quality comparable to high-end commercial microscopes at a cost of less than US$400 for a bright-field system, with an extra US$100 needed for the fluorescence module.

Combinatorial therapy with two pro-coagulants and one osmotic agent reduces the extent of the lesion in the acute phase of spinal cord injury in the rat

Background

Spinal cord injury (SCI) is a complex disease that leads to a motor, sensitive, and vegetative impairment. So far, single therapies are ineffective for treating SCI in humans and a multifactorial therapeutic approach may be required. The aim of this work was to assess the effect of a triple therapy (TT) associating two pro-coagulant therapies (tranexamic acid and fibrinogen) with an anti-edema therapy (hypertonic saline solution), on the extent of the lesion 24 h post-injury.

Methods

The design of this study is a randomized controlled study. The setting of this study is an experimental study.

Male Wistar rats were assigned to receive saline solution for the control group or one of the treatment, or a combination of two treatments or the three treatments (triple therapy group (TT)). Animals were anesthetized and received a weight-drop SCI induced at the level of the 12th thoracic vertebra (Th12). They were treated by single therapies, double therapies, or TT started 5 min after the SCI.

Results

The extent of the lesion was assessed 24 h after injury by spectrophotometry (quantification of parenchymal hemorrhage and blood-spinal cord barrier disruption) and by histology (quantification of spared neuronal tissue).

As compared with the control group, the TT significantly reduced parenchymal hemorrhage (p < 0.05) and improved the total amount of intact neural tissue, measured 24 h later (p = 0.003).

Conclusions

Combinatorial therapy associating two pro-coagulants (tranexamic acid and fibrinogen) with an anti-edema therapy (hypertonic saline solution) reduces the extent of the lesion in the acute phase of spinal cord injury in the rat.

Point-of-care diagnostics to improve maternal and neonatal health in low-resource settings

Each day, approximately 830 women and 7400 newborns die from complications during pregnancy and childbirth. Improving maternal and neonatal health will require bringing rapid diagnosis and treatment to the point of care in low-resource settings. However, to date there are few diagnostic tools available that can be used at the point of care to detect the leading causes of maternal and neonatal mortality in low-resource settings. Here we review both commercially available diagnostics and technologies that are currently in development to detect the leading causes of maternal and neonatal mortality, highlighting key gaps in development where innovative design could increase access to technology and enable rapid diagnosis at the bedside.

3D printed microfluidic mixer for point-of-care diagnosis of anemia

3D printing has been an emerging fabrication tool in prototyping and manufacturing. We demonstrated a 3D microfluidic simulation guided computer design and 3D printer prototyping for quick turnaround development of microfluidic 3D mixers, which allows fast self-mixing of reagents with blood through capillary force. Combined with smartphone, the point-of-care diagnosis of anemia from finger-prick blood has been successfully implemented and showed consistent results with clinical measurements. Capable of 3D fabrication flexibility and smartphone compatibility, this work presents a novel diagnostic strategy for advancing personalized medicine and mobile healthcare.

Beyond Wicking: Expanding the Role of Patterned Paper as the Foundation for an Analytical Platform

While a number of assays for soluble analytes have been developed using paper-based microfluidic devices, the detection and analysis of blood cells has remained an outstanding challenge. In this Feature, we discuss how the properties of paper determine the performance of paper-based microfluidic devices and permit the design of cellular assays, which can ultimately impact disparities in healthcare that exist in limited-resource settings.

Point-of-Care Testing for Anaemia in Children Using Portable Haematocrit Meter: A Pilot Study from Southwest Nigeria and Implications for Developing Countries

Background

Prompt and accurate diagnosis is needed to prevent the untoward effects of anaemia on children. Although haematology analyzers are the gold standard for accurate measurement of haemoglobin or haematocrit for anaemia diagnosis, they are often out of the reach of most health facilities in resource-poor settings thus creating a care gap. We conducted this study to examine the agreement between a point-of-care device and haematology analyzer in determining the haematocrit levels in children and to determine its usefulness in diagnosing anaemia in resource-poor settings.

Methods

EDTA blood samples collected from participants were processed to estimate their haematocrits using the two devices (Mindray BC-3600 haematology analyzer and Portable Mission Hb/Haemotocrit testing system). A pairwise t-test was used to compare the haematocrit (PCV) results from the automated haematology analyzer and the portable haematocrit meter. The agreement between the two sets of measurements was assessed using the Bland and Altman method where the mean, standard deviation and limit of agreement of paired results were calculated.

Results

The intraclass and concordance correlation coefficients were 0.966 and 0.936. Sensitivity and specificity were 97.85% and 94.51% respectively while the positive predictive and negative predictive values were 94.79% and 97.73%. The Bland and Altman`s limit of agreement was −5.5–5.1 with the mean difference being −0.20 and a non-ignificant variability between the two measurements (p = 0.506).

Conclusion

Haematocrit determined by the portable testing system is comparable to that determined by the haematology analyzer. We therefore recommend its use as a point-of-care device for determining haematocrit in resource-poor settings where haematology analyzers are not available.

Anemia prevalence and hemoglobin levels are associated with long-term exposure to air pollution in an older population

BACKGROUND

Anemia, a highly prevalent disorder in elderly populations, is associated with numerous adverse health outcomes, including increased mortality, impaired functional status and cognitive disorders. Approximately two-thirds of anemia in American elderly is caused by chronic inflammation or is unexplained. A potential contributing factor may include air pollution exposures, which have been shown to increase systemic inflammation and affect erythropoiesis. Few studies, however, have investigated the associations of air pollution on hemoglobin levels and anemia.

METHODS

We used linear regression models and modified Poisson regression with robust error variance to examine the associations of particulate matter (PM_2.5) and nitrogen dioxide (NO₂) on hemoglobin concentrations and prevalence of anemia, respectively, among 4121 older Americans enrolled in the National Social Life, Health, and Aging Project. We estimated participant-specific exposures to PM_2.5 using spatio-temporal models, and to NO₂ using nearest measurements from Environmental Protection Agency's Air Quality System. Hemoglobin levels were measured for participants in each of two data collection waves from dried blood spots. Anemia was defined using World Health Organization hemoglobin-based criteria of <13 and <12g/dL for men and women, respectively. Models were adjusted for age, sex, smoking status, race, income, education, neighborhood socioeconomic status, region, urbanicity and medication use. Mediation by C-reactive protein (CRP), a marker of systemic inflammation, was also investigated.

RESULTS

An inter-quartile range (IQR, 3.9μg/m³) increase in the one-year moving average PM_2.5 was positively associated with anemia prevalence (prevalence ratio, or PR 1.33, 95% CI: 1.23, 1.45) and decreases in average hemoglobin of 0.81g/dL (p<0.001). Similarly, an IQR (9.6ppb) increase in NO₂ was associated with anemia prevalence (PR 1.43, 95% CI: 1.25, 1.63) and a decrease in average hemoglobin of 0.81g/dL (p<0.001). Strong dose-response relationships were identified for both pollutants. Mediation of the effect of PM_2.5 by CRP was also identified (p=0.007).

CONCLUSIONS/INTERPRETATIONS

Air pollution exposures were significantly associated with increased prevalence of anemia and decreased hemoglobin levels in a cohort of older Americans. If causal, these associations could indicate that chronic air pollution exposure is an important risk factor for anemia in older adults.

A Rapid and Chemical-free Hemoglobin Assay with Photothermal Angular Light Scattering

Photo-thermal angular light scattering (PT-AS) is a novel optical method for measuring the hemoglobin concentration ([Hb]) of blood samples. On the basis of the intrinsic photothermal response of hemoglobin molecules, the sensor enables high-sensitivity, chemical-free measurement of [Hb]. [Hb] detection capability with a limit of 0.12 g/dl over the range of 0.35 - 17.9 g/dl has been demonstrated previously. The method can be readily implemented using inexpensive consumer electronic devices such as a laser pointer and a webcam. The use of a micro-capillary tube as a blood container also enables the hemoglobin assay with a nanoliter-scale blood volume and a low operating cost. Here, detailed instructions for the PT-AS optical setup and signal processing procedures are presented. Experimental protocols and representative results for blood samples in anemic conditions ([Hb] = 5.3, 7.5, and 9.9 g/dl) are also provided, and the measurements are compared with those from a hematology analyzer. Its simplicity in implementation and operation should enable its wide adoption in clinical laboratories and resource-limited settings.

Emerging point-of-care technologies for sickle cell disease screening and monitoring

INTRODUCTION

Sickle Cell Disease (SCD) affects 100,000 Americans and more than 14 million people globally, mostly in economically disadvantaged populations, and requires early diagnosis after birth and constant monitoring throughout the life-span of the patient. Areas covered: Early diagnosis of SCD still remains a challenge in preventing childhood mortality in the developing world due to requirements of skilled personnel and high-cost of currently available modalities. On the other hand, SCD monitoring presents insurmountable challenges due to heterogeneities among patient populations, as well as in the same individual longitudinally. Here, we describe emerging point-of-care micro/nano platform technologies for SCD screening and monitoring, and critically discuss current state of the art, potential challenges associated with these technologies, and future directions. Expert commentary: Recently developed microtechnologies offer simple, rapid, and affordable screening of SCD and have the potential to facilitate universal screening in resource-limited settings and developing countries. On the other hand, monitoring of SCD is more complicated compared to diagnosis and requires comprehensive validation of efficacy. Early use of novel microdevices for patient monitoring might come in especially handy in new clinical trial designs of emerging therapies.

Measurement of the hematocrit using paper-based microfluidic devices

The quantification of blood cells provides critical information about a patient's health status. Sophisticated analytical equipment, such as hematology analyzers, have been developed to perform these measurements, but limited-resource settings often lack the infrastructure required to purchase, operate, and maintain instrumentation. To address these practical challenges, paper-based microfluidic devices have emerged as a platform to develop diagnostic assays specifically for use at the point-of-care. To date, paper-based microfluidic devices have been used broadly in diagnostic assays that apply immunoassay, clinical chemistry, and electrochemistry techniques. The analysis of cells, however, has been largely overlooked. In this communication, we demonstrate a paper-based microfluidic device that enables the controlled transport of red blood cells (RBCs) and the measurement of the hematocrit-the ratio of RBC packed cell volume to total volume of whole blood. The properties of paper, device treatment, and device geometry affect the overall extent and reproducibility of transport of RBCs. Ultimately, we developed an inexpensive (US$0.03 per device) thermometer-styled device where the distance traveled by RBCs is proportional to the hematocrit. These results provide a foundation for the design of paper-based microfluidic devices that enable the separation and detection of cells in limited-resource settings.

Diagnosis of iron deficiency anemia using density-based fractionation of red blood cells

Iron deficiency anemia (IDA) is a nutritional disorder that impacts over one billion people worldwide; it may cause permanent cognitive impairment in children, fatigue in adults, and suboptimal outcomes in pregnancy. IDA can be diagnosed by detection of red blood cells (RBCs) that are characteristically small (microcytic) and deficient in hemoglobin (hypochromic), typically by examining the results of a complete blood count performed by a hematology analyzer. These instruments are expensive, not portable, and require trained personnel; they are, therefore, unavailable in many low-resource settings. This paper describes a low-cost and rapid method to diagnose IDA using aqueous multiphase systems (AMPS)-thermodynamically stable mixtures of biocompatible polymers and salt that spontaneously form discrete layers having sharp steps in density. AMPS are preloaded into a microhematocrit tube and used with a drop of blood from a fingerstick. After only two minutes in a low-cost centrifuge, the tests (n = 152) were read by eye with a sensitivity of 84% (72-93%) and a specificity of 78% (68-86%), corresponding to an area under the curve (AUC) of 0.89. The AMPS test outperforms diagnosis by hemoglobin alone (AUC = 0.73) and is comparable to methods used in clinics like reticulocyte hemoglobin concentration (AUC = 0.91). Standard machine learning tools were used to analyze images of the resulting tests captured by a standard desktop scanner to 1) slightly improve diagnosis of IDA-sensitivity of 90% (83-96%) and a specificity of 77% (64-87%), and 2) predict several important red blood cell parameters, such as mean corpuscular hemoglobin concentration. These results suggest that the use of AMPS combined with machine learning provides an approach to developing point-of-care hematology.

3D printed auto-mixing chip enables rapid smartphone diagnosis of anemia

Clinical diagnosis requiring central facilities and site visits can be burdensome for patients in resource-limited or rural areas. Therefore, development of a low-cost test that utilizes smartphone data collection and transmission would beneficially enable disease self-management and point-of-care (POC) diagnosis. In this paper, we introduce a low-cost iPOC^3D diagnostic strategy which integrates 3D design and printing of microfluidic POC device with smartphone-based disease diagnosis in one process as a stand-alone system, offering strong adaptability for establishing diagnostic capacity in resource-limited areas and low-income countries. We employ smartphone output (AutoCAD 360 app) and readout (color-scale analytical app written in-house) functionalities for rapid 3D printing of microfluidic auto-mixers and colorimetric detection of blood hemoglobin levels. The auto-mixing of reagents with blood via capillary force has been demonstrated in 1 second without the requirement of external pumps. We employed this iPOC^3D system for point-of-care diagnosis of anemia using a training set of patients (n_anemia = 16 and n_healthy = 6), which showed consistent measurements of blood hemoglobin levels (a.u.c. = 0.97) and comparable diagnostic sensitivity and specificity, compared with standard clinical hematology analyzer. Capable of 3D fabrication flexibility and smartphone compatibility, this work presents a novel diagnostic strategy for advancing personalized medicine and mobile healthcare.

Modelling retinal pulsatile blood flow from video data

Modern day datasets continue to increase in both size and diversity. One example of such 'big data' is video data. Within the medical arena, more disciplines are using video as a diagnostic tool. Given the large amount of data stored within a video image, it is one of most time consuming types of data to process and analyse. Therefore, it is desirable to have automated techniques to extract, process and analyse data from video images. While many methods have been developed for extracting and processing video data, statistical modelling to analyse the outputted data has rarely been employed. We develop a method to take a video sequence of periodic nature, extract the RGB data and model the changes occurring across the contiguous images. We employ harmonic regression to model periodicity with autoregressive terms accounting for the error process associated with the time series nature of the data. A linear spline is included to account for movement between frames. We apply this model to video sequences of retinal vessel pulsation, which is the pulsatile component of blood flow. Slope and amplitude are calculated for the curves generated from the application of the harmonic model, providing clinical insight into the location of obstruction within the retinal vessels. The method can be applied to individual vessels, or to smaller segments such as 2 × 2 pixels which can then be interpreted easily as a heat map.

A Novel, Nondestructive, Dried Blood Spot-Based Hematocrit Prediction Method Using Noncontact Diffuse Reflectance Spectroscopy

Dried blood spot (DBS) sampling is recognized as a valuable alternative sampling strategy both in research and in clinical routine. Although many advantages are associated with DBS sampling, its more widespread use is hampered by several issues, of which the hematocrit effect on DBS-based quantitation remains undoubtedly the most widely discussed one. Previously, we developed a method to derive the approximate hematocrit from a nonvolumetrically applied DBS based on its potassium content. Although this method yielded good results and was straightforward to perform, it was also destructive and required sample preparation. Therefore, we now developed a nondestructive method which allows to predict the hematocrit of a DBS based on its hemoglobin content, measured via noncontact diffuse reflectance spectroscopy. The developed method was thoroughly validated. A linear calibration curve was established after log/log transformation. The bias, intraday and interday imprecision of quality controls at three hematocrit levels and at the lower and upper limit of quantitation (0.20 and 0.67, respectively) were less than 11%. In addition, the influence of storage and the volume spotted was evaluated, as well as DBS homogeneity. Application of the method to venous DBSs prepared from whole blood patient samples (n = 233) revealed a good correlation between the actual and the predicted hematocrit. Limits of agreement obtained after Bland and Altman analysis were -0.076 and +0.018. Incurred sample reanalysis demonstrated good method reproducibility. In conclusion, mere scanning of a DBS suffices to derive its approximate hematocrit, one of the most important variables in DBS analysis.

Validation of a Low-Cost Paper-Based Screening Test for Sickle Cell Anemia

Background

The high childhood mortality and life-long complications associated with sickle cell anemia (SCA) in developing countries could be significantly reduced with effective prophylaxis and education if SCA is diagnosed early in life. However, conventional laboratory methods used for diagnosing SCA remain prohibitively expensive and impractical in this setting. This study describes the clinical validation of a low-cost paper-based test for SCA that can accurately identify sickle trait carriers (HbAS) and individuals with SCA (HbSS) among adults and children over 1 year of age.

Methods and Findings

In a population of healthy volunteers and SCA patients in the United States (n = 55) the test identified individuals whose blood contained any HbS (HbAS and HbSS) with 100% sensitivity and 100% specificity for both visual evaluation and automated analysis, and detected SCA (HbSS) with 93% sensitivity and 94% specificity for visual evaluation and 100% sensitivity and 97% specificity for automated analysis. In a population of post-partum women (with a previously unknown SCA status) at a primary obstetric hospital in Cabinda, Angola (n = 226) the test identified sickle cell trait carriers with 94% sensitivity and 97% specificity using visual evaluation (none of the women had SCA). Notably, our test permits instrument- and electricity-free visual diagnostics, requires minimal training to be performed, can be completed within 30 minutes, and costs about $0.07 in test-specific consumable materials.

Conclusions

Our results validate the paper-based SCA test as a useful low-cost tool for screening adults and children for sickle trait and disease and demonstrate its practicality in resource-limited clinical settings.

Development of a novel smartphone-based application for accurate and sensitive on-field hemoglobin measurement

A smartphone-based app for the accurate and sensitive measurement of hemoglobin was developed.

An accurate and inexpensive color-based assay for detecting severe anemia in a limited-resource setting

Severe anemia is an important cause of morbidity and mortality among children in resource-poor settings, but laboratory diagnostics are often limited in these locations. To address this need, we developed a simple, inexpensive, and color-based point-of-care (POC) assay to detect severe anemia. The purpose of this study was to evaluate the accuracy of this novel POC assay to detect moderate and severe anemia in a limited-resource setting. The study was a cross-sectional study conducted on children with sickle cell anemia in Luanda, Angola. The hemoglobin concentrations obtained by the POC assay were compared to reference values measured by a calibrated automated hematology analyzer. A total of 86 samples were analyzed (mean hemoglobin concentration 6.6 g/dL). There was a strong correlation between the hemoglobin concentrations obtained by the POC assay and reference values obtained from an automated hematology analyzer (r=0.88, P<0.0001). The POC assay demonstrated excellent reproducibility (r=0.93, P<0.0001) and the reagents appeared to be durable in a tropical setting (r=0.93, P<0.0001). For the detection of severe anemia that may require blood transfusion (hemoglobin <5 g/dL), the POC assay had sensitivity of 88.9% and specificity of 98.7%. These data demonstrate that an inexpensive (<$0.25 USD) POC assay accurately estimates low hemoglobin concentrations and has the potential to become a transformational diagnostic tool for severe anemia in limited-resource settings.

Sickle cell detection using a smartphone

Sickle cell disease affects 25% of people living in Central and West Africa and, if left undiagnosed, can cause life threatening "silent" strokes and lifelong damage. However, ubiquitous testing procedures have yet to be implemented in these areas, necessitating a simple, rapid, and accurate testing platform to diagnose sickle cell disease. Here, we present a label-free, sensitive, and specific testing platform using only a small blood sample (<1 μl) based on the higher density of sickle red blood cells under deoxygenated conditions. Testing is performed with a lightweight and compact 3D-printed attachment installed on a commercial smartphone. This attachment includes an LED to illuminate the sample, an optical lens to magnify the image, and two permanent magnets for magnetic levitation of red blood cells. The sample is suspended in a paramagnetic medium with sodium metabisulfite and loaded in a microcapillary tube that is inserted between the magnets. Red blood cells are levitated in the magnetic field based on equilibrium between the magnetic and buoyancy forces acting on the cells. Using this approach, we were able to distinguish between the levitation patterns of sickle versus control red blood cells based on their degree of confinement.

Smartphone dongle for simultaneous measurement of hemoglobin concentration and detection of HIV antibodies

It is traditionally difficult to incorporate two classes of diagnostic tests into a single platform. In this work, we demonstrate a microfluidic-based smartphone dongle that simultaneously measures concentration of hemoglobin and detects HIV antibodies. Specifically, we demonstrate how a previously published immunoassay device, which measured optical density of silver precipitation on gold colloids, can be expanded to quantitatively measure hemoglobin concentration via a colorimetric assay. By lysing whole blood components with CHAPS detergent, we achieved highly reproducible measurement of hemoglobin concentration with the device. We tested this dual test on 38 patient samples from Columbia University Medical Center. Compared with the Hemocue Hb 201+ analyzer, hemoglobin concentrations from our device were accurate within 1.2 g dL(-1), while the HIV immunoassay (in the presence of CHAPS detergent) showed 95% sensitivity and 95% specificity, comparable to our previous studies. This work demonstrates the feasibility of integrating two classes of diagnostic tests (a colorimetric-based quantitative measurement and an immunoassay based on silver precipitation on gold colloids) into a low-cost, fast, and low-power dongle that works with smartphones, and creates a novel dual panel with clinical utility for antenatal-care settings.

Development of inexpensive blood imaging systems: where are we now?

Clinical applications in the developing world, such as malaria and anemia diagnosis, demand a change in the medical paradigm of expensive care given in central locations by highly trained professionals. There has been a recent explosion in optical technologies entering the consumer market through the widespread adoption of smartphones and LEDs. This technology commoditization has enabled the development of small, portable optical imaging systems at an unprecedentedly low cost. Here, we review the state-of-the-field of the application of these systems for low-cost blood imaging with an emphasis on cellular imaging systems. In addition to some promising results addressing specific clinical issues, an overview of the technology landscape is provided. We also discuss several key issues that need to be addressed before these technologies can be commercialized.

Multiplex detection and genotyping of pathogenic bacteria on paper-based biosensor with a novel universal primer mediated asymmetric PCR

Traditionary multiplex asymmetric polymerase chain reaction (PCR) can be applied to detect multiplex target organisms simultaneously, but complex optimizations of primer concentrations and staggered additions of primers are required to achieve equal amplification of multiplex genes. To overcome this shortcoming, we propose a novel method based on multiplex asymmetric PCR and paper-based nucleic acid diagnostics (PBNAD). In the asymmetric PCR, a universal primer was introduced to break the bottlenecks of low sensitivity and self-inhibition among different sets of primers. Amplification using the novel multiplex asymmetric PCR boosted the quantity of single-stranded amplicons, and the amplified products contained the same sequence at the 5' end. Therefore, only one gold nanoparticle-based signal probe was needed for the simultaneous detection of three genes using the PBNAD platform, and the detection signals could be observed with the naked eye. With this highly efficient, novel multiplex asymmetric PCR, as little as 1 pg/μL genomic DNA can be detected. This method can also be applied to genotyping for reliable epidemiological investigations. This proof-of-concept study highlights the potential of the PBNAD platform for cost- and labor-effective applications in the detection of pathogenic bacteria.

A rapid paper-based test for quantifying sickle hemoglobin in blood samples from patients with sickle cell disease

Quantification of sickle hemoglobin (HbS) in patients with sickle cell disease (SCD) undergoing hydroxyurea or chronic transfusion therapy is essential to monitoring the effectiveness of these therapies. The clinical monitoring of %HbS using conventional laboratory methods is limited by high per-test costs and long turnaround times usually associated with these methods. Here we demonstrate a simple, rapid, inexpensive paper-based assay capable of quantifying %HbS in blood samples from patients with SCD. A 20 μL droplet of whole blood and hemoglobin solubility buffer was deposited on chromatography paper. The relative color intensities of regions of the resulting blood stain, determined by automated image analysis, are used to estimate %HbS. We compared the paper-based assay with hemoglobin electrophoresis (comparison method) using blood samples from 88 subjects. The test shows high correlation (R(2)  = 0.86) and strong agreement (standard deviation of difference = 7%HbS) with conventional Hb electrophoresis measurement of %HbS, and closely approximates clinically predicted change in %HbS with transfusion therapy (mean difference 2.6%HbS, n = 5). The paper-based assay can be completed in less than 35 min and has a per-test cost less than $0.25. The assay is accurate across a wide range of HbS levels (10-97%) and hemoglobin concentrations (5.6-12.9 g/dL) and is unaffected by high levels of HbF (up to 80.6%). This study demonstrates the feasibility of the paper-based %HbS assay. The paper-based test could improve clinical care for SCD, particularly in resource-limited settings, by enabling more rapid and less expensive %HbS monitoring.

Portable, Easy-to-Operate, and Antifouling Microcapsule Array Chips Fabricated by 3D Ice Printing for Visual Target Detection

Herein, we proposed a portable, easy-to-operate, and antifouling microcapsule array chip for target detection. This prepackaged chip was fabricated by innovative and cost-effective 3D ice printing integrating with photopolymerization sealing which could eliminate complicated preparation of wet chemistry and effectively resist outside contaminants. Only a small volume of sample (2 μL for each microcapsule) was consumed to fulfill the assay. All the reagents required for the analysis were stored in ice form within the microcapsule before use, which guaranteed the long-term stability of microcapsule array chips. Nitrite and glucose were chosen as models for proof of concept to achieve an instant quantitative detection by naked eyes without the need of external sophisticated instruments. The simplicity, low cost, and small sample consumption endowed ice-printing microcapsule array chips with potential commercial value in the fields of on-site environmental monitoring, medical diagnostics, and rapid high-throughput point-of-care quantitative assay.