Paper-based biosensors as point-of-care diagnostic devices for the detection of cancers: a review of innovative techniques and clinical applications

The development and rapid progression of cancer are major social problems. Medical diagnostic techniques and smooth clinical care of cancer are new necessities that must be supported by innovative diagnostic methods and technologies. Current molecular diagnostic tools based on the detection of blood protein markers are the most common tools for cancer diagnosis. Biosensors have already proven to be a cost-effective and accessible diagnostic tool that can be used where conventional laboratory methods are not readily available. Paper-based biosensors offer a new look at the world of analytical techniques by overcoming limitations through the creation of a simple device with significant advantages such as adaptability, biocompatibility, biodegradability, ease of use, large surface-to-volume ratio, and cost-effectiveness. In this review, we covered the characteristics of exosomes and their role in tumor growth and clinical diagnosis, followed by a discussion of various paper-based biosensors for exosome detection, such as dipsticks, lateral flow assays (LFA), and microfluidic paper-based devices (µPADs). We also discussed the various clinical studies on paper-based biosensors for exosome detection.

Dry Reagent Tests in the 1880s-Dr Pavy's Pellets and Dr Oliver's Papers

BACKGROUND

In the 1880s, concern over the inconvenience of hazardous chemical solutions used for bedside urinalysis sparked an interest in the development of dry reagents for a range of common urine tests.

CONTENT

This article examines the history of Dr Pavy's Pellets and Dr Oliver's Papers, 2 different dry reagent systems developed in the 1880s for bedside urine testing. It sets these developments in the context of the earlier dry chemistry work (e.g., indicator papers) and the subsequent work that led to modern day reagent tablets and dipstick devices.

SUMMARY

Tests based on dry reagents can be traced back to the 1st century, but active development, in the form of indicator papers, dates from the 1600s. In the 1880s, spurred by dissatisfaction with liquid-based bedside urine testing among clinicians, Dr Frederick William Pavy and Dr George Oliver developed dry reagent tests, based on pellets (Dr Pavy's Pellets) and chemically impregnated papers (Dr Oliver's Papers) for urine sugar and urine albumin. These reagents were commercialized by a number of companies and provided in convenient cases (Physician's Pocket Reagent Case). Eventually, these tests lost popularity and were replaced by the type of tablets and dipsticks developed by both Eli Lilly, and the Ames Division of Miles Laboratories (subsequently Bayer, and currently Siemens Healthineers) during the 1940s and 1950s.

Open label feasibility study evaluating D-mannose combined with home-based monitoring of suspected urinary tract infections in patients with multiple sclerosis

OBJECTIVE

To assess the feasibility of using D-mannose, a natural food supplement, in patients with multiple sclerosis (MS) reporting recurrent urinary tract infections (UTIs) as a preventative.

METHODS

A single-center, open-label, feasibility study enrolled patients with MS, using and not using urinary catheters, experiencing recurrent UTIs (≥3/year or ≥2/6 months). Participants were given D-mannose powder 1.5 grams twice daily for 16-weeks and were instructed to monitor suspected UTIs at home using urine dipsticks. Diaries were used to record compliance, number of prescriptions of antibiotics received for UTIs, results of urine dipsticks and cultures.

RESULTS

Overall, 22 patients with MS, median age 50 years (46-59) were enrolled: 10 were not using catheters and 12 were using catheters. The compliance rates for using D-mannose and dipsticks for testing suspected UTIs were 100% and 90.2%, respectively. Sixty-one episodes of suspected UTIs were recorded, 19/61 (31.1%) were confirmed UTIs and 29/61 (47.5%) prescriptions of antibiotics were made. The number of monthly proven UTIs decreased both in catheter users and non-users (P < 0.01). No adverse effects were reported.

CONCLUSION

Using D-mannose in patients with MS experiencing recurrent UTIs and self-monitoring for infections is feasible and safe. Further studies are required to establish efficacy. CinicalTrials.gov (identifier NCT02490046).

Reliability of reagent strips for semi-quantitative measurement of glucosuria in a neonatal intensive care setting

BACKGROUND

Glucosuria in preterm infants is often measured using a visually readable reagent strip, e.g., when monitoring total parenteral nutrition or during sepsis or when treating with corticosteroids. However, the specific circumstances in a neonatal intensive care unit (NICU), such as the use of diapers and the high temperature in incubators, could affect its reliability.

OBJECTIVES

To evaluate the reliability of the semi-quantitative measurement of glucosuria under the specific circumstances of a NICU setting.

METHODS

Nine hundred assessments of artificially supplemented (contrived) urine samples, intended to simulate pathological specimens, were performed under the following varying conditions: environmental temperature (21°C and 34°C); different times of contact of the urine with the diaper; and using two different methods of collecting urine from the diaper. Each reagent strip was read independently by three observers. The test strips scores were categorized as 0, 1+, 2+, 3+, or 4+ in ascending degree of glucosuria.

RESULTS

Agreement was excellent under all the different conditions (temperature, weighted kappa (κ(w)) = 0.92; method of urine collection, κ(w) = 0.88; time, p = 0.266). Inter-observer reliability was very good (multi-rater κ = 0.81). The deviation between the different conditions was seldom larger than one category (2.9%). The reagent strip readings were concordant with the true urinary glucose concentrations in 79.0% of assessments. The discordance was never larger than one category.

CONCLUSION

The reliability of the semi-quantitative measurement of glucosuria in newborn infants using reagent strips is good, even under the conditions of a NICU. Changes in the rating of reagent strips of more than one category are most likely to be beyond measurement error.

Developing clinical rules to predict urinary tract infection in primary care settings: sensitivity and specificity of near patient tests (dipsticks) and clinical scores

BACKGROUND

Suspected urinary tract infection (UTI) is one of the most common presentations in primary care. Systematic reviews have not documented any adequately powered studies in primary care that assess independent predictors of laboratory diagnosis.

AIM

To estimate independent clinical and dipstick predictors of infection and to develop clinical decision rules.

DESIGN OF STUDY

Validation study of clinical and dipstick findings compared with laboratory testing.

SETTING

General practices in the south of England.

METHOD

Laboratory diagnosis of 427 women with suspected UTI was assessed using European urinalysis guidelines. Independent clinical and dipstick predictors of diagnosis were estimated.

RESULTS

UTI was confirmed in 62.5% of women with suspected UTI. Only nitrite, leucocyte esterase (+ or greater), and blood (haemolysed trace or greater) independently predicted diagnosis (adjusted odds ratios 6.36, 4.52, 2.23 respectively). A dipstick decision rule, based on having nitrite, or both leucocytes and blood, was moderately sensitive (77%) and specific (70%); positive predictive value (PPV) was 81% and negative predictive value (NPV) was 65%. Predictive values were improved by varying the cut-off point: NPV was 73% for all three dipstick results being negative, and PPV was 92% for having nitrite and either blood or leucocyte esterase. A clinical decision rule, based on having two of the following: urine cloudiness, offensive smell, and dysuria and/or nocturia of moderate severity, was less sensitive (65%) (specificity 69%; PPV 77%, NPV 54%). NPV was 71% for none of the four clinical features, and the PPV was 84% for three or more features.

CONCLUSIONS

Simple decision rules could improve targeting of investigation and treatment. Strategies to use such rules need to take into account limited negative predictive value, which is lower than expected from previous research.