Urgent Care Conference
October 21-23
Phoenix, Arizona
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November 3-7
Atlanta, Georgia
World Conference on Lung Health
November 11-15
Berlin, Germany
Medica
November 17-20
Düsseldorf, Germany
QBC ParaLens: Scientific Studies
The QBC ParaLens is a remarkable tool for clinical and research applications.
It has been used widely in tropical diagnostics and has shown significant utility for many microbiological assays.
Listed below are abstracts and links for scientific articles that report or discuss the utility of the ParaLens for many different applications.
Minion, J., Sohn, H., and Pai, M. (2009) Light-emitting diode technologies for TB diagnosis: what is on the market? Expert Review of Medical Devices 6(4): 341-345.
Ramsay A, Cuevas LE, Mundy CJF, Nathanson C-M, Chirambo P, et al. (2009) New Policies, New Technologies: Modelling the Potential for Improved Smear Microscopy Services in Malawi. PLoS ONE 4(11): e7760. doi:10.1371/journal.pone.0007760.
"Background: To quantify the likely impact of recent WHO policy recommendations regarding smear microscopy and the introduction of appropriate low-cost fluorescence microscopy on a) case detection and b) laboratory workload.
Methodology/Principal Findings: An audit of the laboratory register in an urban hospital, Lilongwe, Malawi, and the application of a simple modelling framework.
The adoption of the new definition of a smear-positive case could directly increase case detection by up to 28%.
Examining Ziehl-Neelsen (ZN) sputum smears for up to 10 minutes before declaring them negative has previously been shown to increase case detection (over and above that gained by the adoption of the new case definition) by 70% compared with examination times in routine practice.
Three times the number of staff would be required to adequately examine the current workload of smears using ZN microscopy.
Through implementing new policy recommendations and LED-based fluorescence microscopy the current laboratory staff complement could investigate the same number of patients, examining auramine-stained smears to an extent that is equivalent to a 10 minutes ZN smear examination.
Conclusions/Significance: Combined implementation of the new WHO recommendations on smear microscopy and LEDbased fluorescence microscopy could result in substantial increases in smear positive case-detection using existing human resources and minimal additional equipment."
Armstrong, D. (Dec. 2009 / Jan. 2010) LED-based fluoroscopy and the Paralens system: illuminating the future of TB diagnostics. Clinical Laboratory International.
"Tuberculosis is a major cause of morbidity and mortality globally.
The situation is often exacerbated by insensitive diagnostic procedures.
The recent introduction of LED (Light-emitting diode) fluorescent techniques for the rapid identification of AFB (Acid-Fast Bacilli) provides laboratorians and healthcare workers around the globe with a proven sensitive technique for microscopic observation of AFB."
Walter Kuhn, Derek Armstrong, Suzanne Atteberry, Euline Dewbrey, Diane Smith and Nancy Hooper (2010) Usefulness of the Paralens™ Fluorescent Microscope Adaptor for the Identification of Mycobacteria in Both Field and Laboratory Settings
"The presence of acid-fast bacilli (AFB) in laboratories has traditionally been demonstrated using the fluorochrome method, which requires a fluorescent microscope or the Ziehl-Neelsen (ZN) method employing light microscopy.
Low sensitivity of the ZN method and high costs of fluoroscopy make the need for a more effective means of diagnosis a top priority, especially in developing countries where the burden of tuberculosis is high.
The QBC ParaLens™ attachment (QBC Diagnostics Inc., Port Matilda, PA) is a substitute for conventional fluoroscopy in the identification of AFB.
To evaluate the efficacy of the ParaLens LED (light-emitting diode) system, the authors performed a two-part study, looking at usefulness, functionality and durability in urban/rural health clinics around the world, as well as in a controlled state public health laboratory setting.
In the field, the ParaLens was durable and functioned well with various power sources and lighting conditions.
Results from the state laboratory indicated agreement between standard fluorescent microscopy and fluorescent microscopy using the ParaLens.
This adaptor is a welcome addition to laboratories in resource-limited settings as a useful alternative to conventional fluoroscopy for detection of mycobacterial species."
Malaria
Anthony, R.L., Bangs, M.J., Anthony, J.M., and Purnomo. (1992) On-site diagnosis of Plasmodium falciparum, P. vivax, and P. malariae by using the Quantitative Buffy Coat system. Journal of Parasitoogyl. 78(6):994-8.
"The Quantitative Buffy Coat (QBC) system was used for the detection and identification of malaria parasites in blood specimens from 570 residents of Oksibil, an isolated highland valley in the eastern Jayawijaya Mountains of Irian Jaya (Indonesian New Guinea).
The availability of a battery-powered centrifuge and a fiberoptic Paralens enabled us to complete and interpret the assay in this remote environment.
Of 322 QBC tubes examined for 2-4 min each, results of 295 (92%) concurred with findings on the matched Giemsa-stained thick smear (GTS).
The 27 discrepant results included 13 QBC+/GTS- that, upon reexamination, were found to be GTS+.
When using the corrected GTS results as the standard, the sensitivity and specificity of the QBC were 94% and 96%, respectively.
Because electricity was available only 3 hr per day, it was decided to decrease the examination for an additional 248 QBC to a maximum of 90 sec per tube.
This shortened inspection time resulted in a reduction of sensitivity to 53% but specificity was preserved at 89%.
Forty-two of 45 conflicting results, QBC-/GTS+ from cases of light Plasmodium falciparum infections with < 1 trophozoite or gametocyte per field, were resolved by reexamination of the QBC in the laboratory.
Tubes held at 4 C could be reexamined, without noticeable loss of fluorescence, for at least 6 wk after collection.
Despite some difficulty in the identification of Plasmodium species, it was concluded that the QBC is an easy, sensitive method for the rapid diagnosis of malaria in the field and that it provides the inexperienced microscopist with an additional means for on-site identification of individuals needing treatment."
Trypanosomiasis
Bailey, J.W. and Smith, D.H. (1994) The quantitative buffy coat for the diagnosis of trypanosomes. Tropical Doctor 24(2):54-6.
"The use of quantitative buffy coat (QBC) tubes developed for malaria diagnosis is described in the diagnosis of African trypanosomiasis.
One hundred and thirty-four patients with Trypanosoma gambiense were examined using QBC plus either haematocrit (HCT) or mini anion exchange centrifugation (MAEC) or both.
QBC was the only method that detected all 134 patients.
QBC proved to be the most sensitive diagnostic test for the detection of trypanosomes in blood.
It is simple to use, gives fast results and would be a useful test at the district hospital level."
Filariasis
Freedman, D.O. and Berry, R.S. (1992) Rapid Diagnosis of Bancroftian Filariasis by Acridine Orange Staining of Centrifuged Parasites. American Journal of Tropical Medicine and Hygiene 47(6): 787-793.
"A rapid diagnostic test for detection of microfilaremia using a microhematocrit tube precoated with acridine orange (the Quantitative Buffy Coat [QBC] tube) was compared with a conventional 50 microliters-thick blood film (TF) in 119 volunteers in an area of Recife, Brazil that was endemic for Wuchereria bancrofti.
Both the QBC and the TF techniques were 100% specific, and thus positive predictive values were equal at 100% for each technique in all subjects studied.
Both techniques had equal negative predictive values of 100% in subjects with microfilarial counts > 100 per milliliter (mf/ml).
Counts < 20 mf/ml are below a cutoff equal to the calculated limit of sensitivity of each of the two techniques.
For those individuals with counts between 20 and 99 mf/ml, negative predictive values were, for practical diagnostic purposes, equivalent at 97.5% for the QBC technique and 99.0% for the TF.
Because the QBC technique has predictive values as high as conventional TF, the convenience and rapidity of the technique will make the QBC technique a desirable alternative diagnostic method in those clinical settings where the equipment is available.
A positive result will be available in less than six min after obtaining the specimen in individuals with counts < 100 mf/ml, and individuals with lower or no microfilaremia will have a result within 6-12 min."
Pneumocystis Carinii
A. R. Mattia, M. A. Waldron, and L. S. Sierra. (1993) Use of the UV ParaLens adapter as an alternative to conventional fluorescence microscopy for detection of Pneumocystis carinii in direct immunofluorescent monoclonal antibody-stained pulmonary specimens. Journal of Clinical Microbiology 31(3): 720-721.
"The UV ParaLens light microscope adapter offers a useful and cost-effective alternative to conventional fluorescence microscopy for Pneumocystis carinii identification, particularly in AIDS patients.
In a blinded study, in which 153 pulmonary specimens were examined for P. carinii by direct immunofluorescence, 40 of 42 specimens positive by fluorescence microscopy were also positive by ParaLens.
No false positives were observed."
Babesiosis
Mattia, A.R., Waldron, M.A., and Sierra, L.S. (1993)Use of the Quantitative Buffy Coat system for detection of parasitemia in patients with babesiosis. Journal of Clinical Microbiology 31(10):2816-8.
"Quantitative Buffy Coat analysis and blood smears were performed on a total of 47 blood samples.
The technique showed 100% correlation with the blood smears in 9 samples containing babesia and 10 samples containing malaria, with some differential features distinguishing the two infections.
Quantitative Buffy Coat analysis provides a simple and rapid method for the detection of parasitemia in cases of babesiosis."
Leptospirosis
Kramer, K.J., Pang, L.W., Minette, H.P., and Perrone, J.B. (1994) Evaluation of the quantitative buffy coat analysis (QBC) system for the detection of Leptospira in human blood. Southeast Asian Journal of Tropical Medicine and Public Health 25(4):788-9.
Rabies
Polsuwan, C., Lumlertdaecha, B., Tepsumethanon, W., and Wilde, H. (1992) Using the UV ParaLens adapter on a standard laboratory microscope for fluorescent rabies antibody detection. Transactions of the Royal Society of Tropical Medicine and Hygiene 86(1):107.
