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References
UNAIDS/WHO. AIDS epidemic update [online], (UNAIDS/WHO, Geneva, Switzerland, 2007).
Plate, D. K. Evaluation and implementation of rapid HIV tests: the experience in 11 African countries. AIDS Res. Hum. Retroviruses 23, 1491–1498 (2007).
Peeling, R. W, Smith, P. G. & Bossuyt, P. M. A guide for diagnostic evaluations. Nature Rev. Microbiol. 4, S2–6 (2006).
Petti, C. A., Polage, C. R., Quinn, T. C., Ronald, A. R. & Sande, M. A. Laboratory medicine in Africa: a barrier to effective health care. Clin. Infect. Dis. 42, 377–382 (2006).
Glencross, D. K., Stevens, G., Scott, L. E., Mendelow, B. V. & Stevens, W. The challenge of laboratory monitoring of HIV. S. Afr. Med. J. 92, 248 (2002).
Glencross, D. K., Mendelow., B. V. & Stevens, W. S. Laboratory monitoring of HIV/AIDS in a resource-poor setting. S. Afr. Med. J. 93, 262–263 (2003).
Stevens, W. S. et al. Affordable HIV diagnosis and monitoring for scaling up ARV treatment programs. S. Afr. J. HIV Med. 20, 38–41 (2005).
Mellors, J. W. et al. Plasma viral load and CD4+ lymphocytes as prognostic markers of HIV-1 infection. Ann. Intern. Med. 126, 946–954 (1997).
Fahey, J. L. et al. The prognostic value of cellular and serologic markers in infection with human immunodeficiency virus type 1. N. Engl. J. Med. 322, 166–172 (1990).
Panel on Antiretroviral Guidelines for Adults and Adolescents, Department of Health and Human Services. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents [online], (Department of Health and Human Services, Washington, USA, 2008).
WHO. Patient monitoring guidelines for HIV care and antiretroviral therapy (ART) [online], (WHO, Geneva, Switzerland, 2004).
Gazzard, B. British HIV Association (BHIVA) guidelines for the treatment of HIV-infected adults with antiretroviral therapy. HIV Med. 7, 487–503 (2006).
Glencross, D. K., Scott, L. E., Jani, I. V., Barnett, D. & Janossy, G. CD45-assisted PanLeucogating for accurate, cost-effective dual-platform CD4+ T-cell enumeration. Cytometry 50, 69–77 (2002).
Mandy, F. F., Bergeron, M. & Minkus, T. Evolution of leukocyte immunophenotyping as influenced by the HIV/AIDS pandemic: a short history of the development of gating strategies for CD4+ T-cell enumeration. Cytometry 30, 157–165 (1997).
Stewart, C. C. & Steinkamp, J. A. Quantitation of cell concentration using the flow cytometer. Cytometry 2, 238–243 (1982).
Valet, G. A new method for fast blood cell counting and partial differentiation by flow cytometry. Blut 49, 83–90 (1984).
Connelly, M. C. et al. Standardization of absolute CD4+ lymphocyte counts across laboratories: an evaluation of the Ortho CytoronAbsolute flow cytometry system on normal donors. Cytometry 22, 200–210 (1995).
Mercolino, T. J. et al. Immunologic differentiation of absolute lymphocyte count with an integrated flow cytometric system: a new concept for absolute T cell subset determinations. Cytometry 22, 48–59 (1995).
Reimann, K. A. et al. Multisite comparison of CD4 and CD8 T-lymphocyte counting by single- versus multiple-platform methodologies: evaluation of Beckman Coulter flow-count fluorospheres and the tetraONE system.The NIAID DAIDS New Technologies Evaluation Group. Clin. Diagn. Lab. Immunol. 7, 344–351 (2000).
Schnizlein-Bick, C. T., Spritzler, J., Wilkening, C. L., Nicholson, J. K. & O'Gorman, M. R. Evaluation of TruCount absolute-count tubes for determining CD4 and CD8 cell numbers in human immunodeficiency virus-positive adults. Site Investigators and The NIAID DAIDS New Technologies Evaluation Group. Clin. Diagn. Lab. Immunol. 7, 336–343 (2000).
Janossy, G., Jani, I. & Gohde, W. Affordable CD4(+) T-cell counts on 'single-platform' flow cytometers I. Primary CD4 gating. Br. J. Haematol. 111, 1198–1208 (2000).
Glencross, D. K. et al. Large-scale affordable PanLeucogated CD4+ testing with proactive internal and external quality assessment: in support of the South African national comprehensive care, treatment and management programme for HIV and AIDS. Cytometry B Clin. Cytom. 74B (Suppl. 1), S40–S51 (2008).
Storie, I. et al. Flow rate calibration II: a clinical evaluation study using PanLeucoGating as a single-platform protocol. Cytometry 55, 8–13 (2003).
Barnett, D., Granger, V., Whitby, L., Storie, I. & Reilly, J. T. Absolute CD4+ T-lymphocyte and CD34+ stem cell counts by single-platform flow cytometry: the way forward. Br. J. Haematol. 106, 1059–1062 (1999).
Gratama, J. W., Kraan, J., Keeney, M., Granger, V. & Barnett, D. Reduction of variation in T-cell subset enumeration among 55 laboratories using single-platform, three or four-color flow cytometry based on CD45 and SSC-based gating of lymphocytes. Cytometry 50, 92–101 (2002).
CLSI. Evaluation of precision performance of quantitative measurement methods. Approved guideline — second edition. NCCLS document EP5-A2 [online], (CLSI, Wayne, Pennysylvania, USA, 2004).
Mandy, F. F., Nicholson, J. K. & McDougal, J. S. Guidelines for performing single-platform absolute CD4+ T-cell determinations with CD45 gating for persons infected with human immunodeficiency virus. Morbid. Mortal. Wkly Rep. 52, 1–13 (2003).
Barnett, D. et al. Guidelines for the enumeration of CD4+ T lymphocytes in immunosuppressed individuals. Clin. Lab. Haematol. 19, 231–241 (1997).
Mandy, F., Nicholson, J., Autran, B. & Janossy, G. T-cell subset counting and the fight against AIDS: reflections over a 20-year struggle. Cytometry 50, 39–45 (2002).
Whitby, L. et al. Quality control of CD4+ T-lymphocyte enumeration: results from the last 9 years of the United Kingdom National External Quality Assessment Scheme for Immune Monitoring (1993–2001). Cytometry 50, 102–110 (2002).
FDA. Food and Drugs Chapter 1 — Food and Drug Administration Department of Health and Human Services Subchapter H — Medical Devices Part 820 Quality System Regulation [online], (FDA, Rockville, Maryland, USA, 2007).
Stevens, W. Good clinical laboratory practice (GCLP): the need for a hybrid of good laboratory practice and good clinical practice guidelines/standards for medical testing laboratories conducting clinical trials in developing countries. Qual. Assur. 10, 83–89 (2003).
Banoo, S. et al. Evaluation of diagnostic tests for infectious diseases: general principles. Nature Rev. Microbiol. 4, S20–32 (2006).
Balakrishnan, P. et al. An inexpensive, simple, and manual method of CD4 T-cell quantitation in HIV-infected individuals for use in developing countries. J. Acquir. Immune Defic. Syndr. 36, 1006–1010 (2004).
Carella, A. V., Moss, M. W., Provost, V. & Quinn, T. C. A manual bead assay for the determination of absolute CD4+ and CD8+ lymphocyte counts in human immunodeficiency virus-infected individuals. Clin. Diagn. Lab. Immunol. 2, 623–625 (1995).
Diagbouga, S. et al. Successful implementation of a low-cost method for enumerating CD4+ T lymphocytes in resource-limited settings: the ANRS 12-26 study. AIDS 17, 2201–2208 (2003).
Didier, J. M. et al. Comparative assessment of five alternative methods for CD4+ T-lymphocyte enumeration for implementation in developing countries. J. Acquir. Immune Defic. Syndr. 26, 193–195 (2001).
Imade, G. E. et al. Comparison of a new, affordable flow cytometric method and the manual magnetic bead technique for CD4 T-lymphocyte counting in a northern nigerian setting. Clin. Diagn. Lab. Immunol. 12, 224–227 (2005).
Karcher, H., Bohning, D., Downing, R., Mashate, S. & Harms, G. Comparison of two alternative methods for CD4+ T-cell determination (Coulter manual CD4 count and CyFlow) against standard dual platform flow cytometry in Uganda. Cytometry B Clin. Cytom. 70B, 163–169 (2006).
Landay, A. et al. A rapid manual method for CD4+ T-cell quantitation for use in developing countries. AIDS 7, 1565–1568 (1993).
Lopez, A. et al. Enumeration of CD4(+) T-cells in the peripheral blood of HIV-infected patients: an interlaboratory study of the FACSCount system. Cytometry 38, 231–237 (1999).
Strauss, K. et al. Performance evaluation of the FACSCount System: a dedicated system for clinical cellular analysis. Cytometry 26, 52–59 (1996).
Balakrishnan, P. et al. A reliable and inexpensive EasyCD4 assay for monitoring HIV-infected individuals in resource-limited settings. J. Acquir. Immune Defic. Syndr. 43, 23–26 (2006).
Pattanapanyasat, K. et al. Evaluation of a single-platform microcapillary flow cytometer for enumeration of absolute CD4+ T-lymphocyte counts in HIV-1 infected Thai patients. Cytometry B Clin. Cytom. 72B, 387–396 (2007).
Fryland, M. et al. The Partec CyFlow Counter could provide an option for CD4+ T-cell monitoring in the context of scaling-up antiretroviral treatment at the district level in Malawi. Trans. Roy. Soc. Trop. Med. Hyg. 100, 980–985 (2006).
Zijenah, L. S. et al. Affordable flow cytometry for enumeration of absolute CD4+ T-lymphocytes to identify subtype C HIV-1 infected adults requiring antiretroviral therapy (ART) and monitoring response to ART in a resource-limited setting. J. Transl. Med. 4, 33 (2006).
Dieye, T. N. et al. Evaluation of an affordable instrument for absolute CD4 counting in resource-poor settings against two reference clinical flow cytometers. Antiviral Ther. 8 (Suppl. 1) Abstract 1126 (2003).
Scott, L. E., Hansen, P., Glencross, D. K., & Stevens, W. PointCARE CD4 testing: the new kid on the block, Abstract 742, session 126. 12th Conference on Retroviruses and Opportunistic infections (Boston, USA, 2005).
Glencross, D. K., Aggett, H. M., Stevens, W. S. & Mandy, F. African regional external quality assessment for CD4 T-cell enumeration: development, outcomes, and performance of laboratories. Cytometry B Clin. Cytom. 74B (Suppl. 1), S69–79 (2008).
Bergeron, M., Houle, G., Azevedo, L., Grangerrio, A. & Mandy, F. F. The impact of single platform absolute counting technology with a linage specific marker and an external quality assessment program. Abstract B12532. AIDS 2006 — XVI International AIDS Conference (Bangkok, Thailand, 2006).
Pattanapanyasat, K., Sukapirom, K., Kowawisatsut, L. & Thepthai, C. New BD FACSCount CD4 reagent system for simultaneous enumeration of percent and absolute CD4 T-lymphocytes in HIV-1-infected pediatric patients. Cytometry B Clin. Cytom. 74B (Suppl. 1) S98–106 (2008).
CLSI. User verification of performance for precision and trueness. Approved guideline—second edition. CLSI document EP15-A2 (CLSI, Wayne, Pennysylvania, USA, 2005).
International Organization for Standardization. Statistics — Vocabulary and symbols — Part 1: General statistical terms and terms used in probability (ISO-3534-1). (International Organization for Standardization, Geneva, Switzerland, 1993)
Denny, T. N. et al. NIAID-DAIDS Immunology Quality Assessment Program. A North American multilaboratory study of CD4 counts using flow cytometric panLeukogating (PLG): a NIAID-DAIDS Immunology Quality Assessment Program Study. Cytometry B Clin. Cytom. 74B (Suppl. 1) S52–64 (2008).
Storie, I. et al. Perfect count: a novel approach for the single platform enumeration of absolute CD4+ T-lymphocytes. Cytometry B Clin. Cytom. 57, 47–52 (2004).
CLSI. Preliminary evaluation of quantitative clinical laboratory measurement procedures. Approved guideline — third edition. CLSI document EP10-A3 (CLSI, Wayne, Pennysylvania, USA, 2006).
Sokal, R. R & Braumann, C. A. Significance tests for coefficients of variation and variability profiles. Syst. Zool. 29, 50–66 (1980).
Haldane, J. B. S. The measurement of variation. Evolution 9, 484 (1955).
Mandy, F., Bergeron, M., Houle, G., Bradley, J. & Fahey, J. Impact of the international program for Quality Assessment and Standardization for Immunological Measures Relevant to HIV/AIDS: QASI. Cytometry 50, 111–116 (2002).
Pattanapanyasat, K. et al. Thailand program for quality assessment and standardization for flow cytometric determination of CD4 T-lymphocyte counts for persons with HIV/AIDS. Abstract MoPeB3179. 15th International Conference on AIDS (Bangkok, Thailand, 2004).
Levey, S. & Jennings, E. R. The use of control charts in the clinical laboratory. Am. J. Clin. Pathol. 20, 1059–1066 (1950).
Brando, B. et al. Cytofluorometric methods for assessing absolute numbers of cell subsets in blood. European Working Group on Clinical Cell Analysis. Cytometry 42, 327–346 (2000).
Bergeron, M. et al. Stability of currently used cytometers facilitates the identification of pipetting errors and their volumetric operation: “time” can tell all. Cytometry B Clin. Cytom. 52, 37–39 (2003).
Scott, L. E. & Glencross, D. K. Monitoring reproducibility of single analysis, single platform CD4 cell counts in a high volume, low resource laboratory setting using sequential bead count rates. Cytometry B Clin. Cytom. 67, 31–32 (2005).
Coetzee, L. M., Scott, L. E., Lawrie, D., Glencross, D. K. & Stevens, W. Evaluation of pipetting methodology to assess precision and accuracy of single platform PLG CD4 enumeration. Abstract P32. 2nd South African AIDS Meeting (Durban, South Africa, 2005).
Bland, J. M. & Altman, D. G. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1, 307–310 (1986).
Scott, L. E., Galpin, J. S. & Glencross, D. K. Multiple method comparison: statistical model using percentage similarity. Cytometry B Clin. Cytom. 54B, 46–53 (2003).
Pollock, M. A. et al. Method comparison — a different approach. Ann. Clin. Biochem. 29, 556–560 (1992).
Bossuyt, P. M. et al. Towards complete and accurate reporting of studies of diagnostic accuracy: the STARD initiative. Standards for Reporting of Diagnostic Accuracy. Clin. Chem. 49, 1–6 (2003).
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CD4 enumeration technologies (PDF 389 kb)
Glossary
- Accuracy
-
A general term used to describe how similar the results obtained for individual specimens with a new CD4 assay are to the results obtained with a reference CD4 assay. Measures of accuracy include bias and misclassification probabilities.
- Bias
-
A measure of how much the CD4 count that is obtained using a new assay differs from the CD4 count that is obtained using a reference assay when the same specimen is analysed using both assays. (Bias need not be constant over the clinically important range of CD4 counts, and need not be the same for different laboratories using the same reference and new technologies.)
- Clinically important range
-
The clinically important range (CIR) of CD4 counts includes most of the CD4 counts (obtained using the reference technology) from HIV-positive patients in a particular locality (clinic, hospital, country or region) for whom a CD4 assay is carried out to determine whether to initiate therapy (antiretroviral therapy or prophylaxis for opportunistic infections). The CIR should include the relevant CD4 count cut-offs as well as a reasonable margin around these cut-offs.
- Coefficient of variation
-
The coefficient of variation (CV) is usually defined as the ratio of the standard deviation to the mean, which is usually estimated as the standard deviation divided by the average. This is often multiplied by 100 and expressed as a percentage (CV%).
- Mean
-
The average value of a random variable, X. The most common estimate of the mean is the average of all the observations.
- Median
-
The value m (of a continuous random variable, X) such that the probability that X is less than m is one half.
- Misclassification probabilities
-
The upward and/or downward misclassification probability can be calculated for a particular cut-off, C. Among specimens with a CD4 count (obtained using the reference technology) which is less than C, the upward misclassification probability is defined as the percentage of specimens for which the CD4 count (obtained using the new technology) is greater than or equal to C (this is analogous to definition of 1 minus the sensitivity in a diagnostic test with only two values: the patient has the disease and the patient does not have the disease). Among specimens with a CD4 count (obtained using the reference technology) which is greater than or equal to C, the downward misclassification probability is defined as the percentage of specimens for which the CD4 count (obtained using the new technology) is less than C (this is analogous to definition of 1 minus the specificity in a diagnostic test with only two values: the patient has the disease and the patient does not have the disease).
- Percentage (p) range
-
The difference between two percentiles that include p% of the range of a random variable; this need not be the middle p%. For example, the difference between the 100th percentile (maximum) and the 10th percentile is a 90 percentile range, as is the difference between the 95th percentile and the 5th percentile.
- Precision
-
Precision (also known as reproducibility) is a general term for how close the results on replicate specimens are (using a single assay technology). Several sorts of precision can be relevant, including within-technician, between-technician, within-laboratory and between-laboratory precision. Measures of precision include the standard deviation, coefficient of variation, interquartile range and percentage (p) range.
- Standard deviation
-
The standard deviation of a distribution (σ for a true value and s for an estimated value) is the positive square root of the variance. This should not be confused with the standard deviation of the mean (sometimes called the standard error); the standard error is the standard deviation divided by the square root of the number of observations.
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Stevens, W., Gelman, R., Glencross, D. et al. Evaluating new CD4 enumeration technologies for resource-constrained countries. Nat Rev Microbiol 6 (Suppl 11), S29–S38 (2008). https://doi.org/10.1038/nrmicro2000
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DOI: https://doi.org/10.1038/nrmicro2000
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