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At least 127 records · Page 7Linked to original sources

PubMed2003

Comparison of the sulforhodamine B assay and the clonogenic assay for in vitro chemoradiation studies.

PURPOSE: Since there is a growing interest in preclinical research on interactions between radiation and cytotoxic agents, this study focused on the development of an alternative to the very laborious clonogenic assay (CA). METHODS: The colorimetric sulforhodamine B (SRB) assay was compared to the clonogenic assay for radiosensitivity testing in two lung cancer cell lines (A549, H292), one colon cancer cell line (HT-29) and one breast cancer cell line (MCF-7). In addition, the combination of the radiosensitizing agent gemcitabine and radiation was investigated with both assays. RESULTS: The dose-response curves obtained with the SRB assay and the CA were very similar up to 6 Gy. The radiosensitivity parameters (SF(2), alpha, beta, MID and ID(50)) obtained from the SRB assay and the CA were not significantly different between H292, A549 and MCF-7 cells. The radiation dose-response curves for A549 and H292 cells pretreated with 4 n M gemcitabine for 24 h clearly showed a radiosensitizing effect with both assays. The dose-enhancement factors obtained with the SRB assay and the CA were 1.80 and 1.76, respectively, for A549 cells, and 1.52 and 1.41 for H292 cells. CONCLUSIONS: The SRB assay was shown to be as useful as the more traditional CA for research on chemotherapy/radiotherapy interactions in cell lines with moderate radiosensitivity. This assay will be used for more extensive in vitro research on radiosensitizing compounds in these cell lines.

Breast Neoplasms↗

PubMed1995

No evidence of the hook effect in peritoneal fluid CA 125 measurement using immunoenzymatic second generation assays: comparison with immunoradiometric assays.

OBJECTIVE: To monitor the occurrence of the hook effect in measurements of peritoneal fluid CA 125 levels using two different immunoenzymatic second generation assays (ETI-II and EIA-II), and to compare these results with those obtained using the respective immunoradiometric versions of the assays (IRMA-II and ELSA-II). STUDY DESIGN: CA 125 levels were determined in peritoneal fluid and serum samples obtained from 45 women with gynecological diseases. The assays were carried out using IRMA-II and ETI-II (Sorin Biomedica) and ELSA-II and EIA-II (CIS Bio International) assays. Occurrence of the hook effect and linearity of the assays were evaluated. Statistical analyses were performed by Wilcoxon's test and linear regression analysis. RESULTS: Undiluted peritoneal fluids, assayed for their CA 125 content, showed falsely underestimated values of the antigen when IRMA-II and ELSA-II assays were performed. The phenomenon disappeared only at high dilutions of the sample (> 50). Conversely, immunoenzymatic ETI-II and EIA-II assays performed on undiluted peritoneal fluids did not show underestimated CA 125 values. CA 125 values obtained by immunoenzymatic assay were lower than those obtained using their respective immunoradiometric versions at a dilution of 1:100 (P < 0.001). A good correlation was observed between ELSA-II and EIA-II (r = 0.929) CA 125 values. CONCLUSION: The EIA-II immunoenzymatic assay appears to be more suitable for CA 125 measurement in peritoneal fluid in that it is not subject to the hook effect and its results correlated well with those obtained via its immunoradiometric version.

Ascitic Fluid↗

PubMed2000

Quantitation of antigen-reactive T cells in peripheral blood by IFNgamma-ELISPOT assay and chromium-release assay: a four-centre comparative trial.

The ELISPOT assay is increasingly being used for the monitoring of the induction of antigen-reactive T cells in cancer vaccination trials. In order to evaluate the reliability of T cell frequency analysis with the ELISPOT assay, a comparative study was performed in four European laboratories. Six samples from healthy subjects were analyzed for the frequency of influenza-reactive CD8+ T cells in peripheral blood mononuclear cells (PBMC) by IFNgamma-ELISPOT assay. In addition, one laboratory determined cytotoxic T cell precursor (CTL) frequencies in these samples by limiting dilution chromium-release assay (LDA), and three laboratories performed a variant of the LDA, the multiple microculture assay (MMA). Consistent frequencies of influenza peptide-reactive T cells were obtained with the ELISPOT assay in all four laboratories. The numbers detected by ELISPOT assay correlated closely with those determined by LDA. In contrast, the frequencies obtained with the MMA differed considerably and showed little correlation with the other two assays. This study shows that it is possible to use the ELISPOT assay to determine with reliability antigen-reactive T cells in a multicenter setting. We suggest that this assay may be suitable for monitoring cancer vaccine trials.

Antigens, Viral↗

PubMed1995

Immunohistochemical assay for epidermal growth factor receptor on paraffin-embedded sections: validation against ligand-binding assay and clinical relevance in breast cancer.

Epidermal growth factor receptor (EGFR) has been the subject of much research since it was first described as a prognostic factor in breast cancer. The assay methods used and results obtained vary widely between studies. In this study 88 primary breast cancers were assayed for EGFR using a novel immunohistochemical assay performed on paraffin-embedded sections. The monoclonal antibody used was raised against purified, denatured EGFR, reacts with an epitope on the external domain and does not interfere with ligand binding. Twenty-two per cent of the tumours were EGFR positive using this assay. The results obtained were significantly correlated with those obtained by ligand-binding assay (r = 0.621, P = 0.011). The concordance rate was 82% (P < 0.001). The majority of discordant results could be explained by the presence of benign breast tissue and other non-malignant elements which could be seen to express EGFR on the immunohistochemical assay and were excluded from the score for this, but would be incorporated into ligand-binding assay results. The well-established inverse relationship between EGFR (as measured by this assay) and oestrogen receptor (ER) was seen (chi 2 = 24.9, P < 0.0001). In addition, in this exploratory study on a limited tumour set, EGFR was a significant adverse prognostic factor (on univariate but not multivariate analysis) for both relapse-free survival (P = 0.02) and overall survival (P = 0.03) when measured by this immunohistochemical assay, but was not significant when measured by ligand-binding assay.

Adult↗

PubMed1990

Comparison of in vitro anticancer-drug-screening data generated with a tetrazolium assay versus a protein assay against a diverse panel of human tumor cell lines.

The National Cancer Institute (NCI) is implementing a large-scale in vitro drug-screening program that requires a very efficient automated assay of drug effects on tumor cell viability or growth. Many laboratories worldwide have adopted a microculture assay based on metabolic reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). However, because of certain technical advantages to use of the protein-binding dye sulforhodamine B (SRB) in a large-scale screening application, a detailed comparison of data generated by each type of assay was undertaken. The MTT and SRB assays were each used to test 197 compounds, on simultaneous days, against up to 38 human tumor cell lines representing seven major tumor categories. On subsequent days, 38 compounds were retested with the SRB assay and 25 compounds were retested with the MTT assay. For each of these three comparisons, we tabulated the differences between the two assays in the ratios of test group values to control values (T/C) for cell survival; calculated correlation coefficients for various T/C ratios; and estimated the bivariate distribution of the values for IC50 (concentration of drug resulting in T/C values of 50%, or 50% growth inhibition) for the two assays. The results indicate that under the experimental conditions used and within the limits of the data analyses, the assays perform similarly. Because the SRB assay has practical advantages for large-scale screening, however, it has been adopted for routine use in the NCI in vitro antitumor screen.

Antineoplastic Agents↗

PubMed1993

Analysis of discordant test results among five second-generation assays for anti-hepatitis C virus antibodies also tested by polymerase chain reaction-RNA assay and other laboratory and clinical tests for hepatitis.

The diagnostic performances of five commercially available second-generation assays for anti-hepatitis C virus antibody, two enzyme-linked immunosorbent assays, one enzyme immunoassay, and two particle agglutination assays (passive hemagglutination assay and particle agglutination assay), were evaluated. Among 104 samples from healthy subjects and 300 consecutive samples from patient ordered for routine determinations of anti-hepatitis C virus antibody in serum, assay results showed variable degrees of discordance for 17 samples (4.2%). These 17 samples were further tested by an immunoblot assay, the polymerase chain reaction-RNA assay, and the hemagglutination inhibition assay. Four of the 17 samples were regarded as true positive, since all supplementary assays and clinical data indicated active hepatitis C virus infection. Another five samples were considered false positive because no confirmatory evidence was obtained from the laboratory analysis or clinical data. The remaining eight samples were negative for hepatitis C virus RNA, but the results of the other supplementary tests were indeterminate. Some of these samples with indeterminate results may have been from patients with subclinical cases of disease who spontaneously recovered from hepatitis with persistent anti-hepatitis C virus antibody in their sera.

Adult↗

PubMed1994

Comparison of peptide enzyme-linked immunosorbent assay and radioimmunoprecipitation assay with in vitro-translated proteins for detection of serum antibodies to human papillomavirus type 16 E6 and E7 proteins.

Antibodies to human papilloma virus (HPV) type 16 (HPV-16) E6 and E7 proteins in serum are markers for HPV-associated invasive cervical carcinoma. We compared two assays, a radioimmunoprecipitation assay with in vitro-translated HPV-16 E6 and E7 proteins and an enzyme-linked immunosorbent assay (ELISA) with E6 and E7 synthetic peptides, for their abilities to discriminate serologically between patients with invasive cervical cancer and controls. Among the patients, antibody prevalences were higher by the E6 radioimmunoprecipitation assay (55.7%) than by the E6 peptide ELISA (15.5%), but among the controls, they were lower by the radioimmunoprecipitation assay (1.7%) than by the E6 peptide ELISA (5%). For E7, antibody prevalences among the patients were comparable by the radioimmunoprecipitation assay (43%) and the peptide ELISA (41%), but among the controls they were higher by the E7 peptide ELISA (17.4%) than by the radioimmunoprecipitation assay (4.1%). There was good agreement between the E7 radioimmunoprecipitation assay and the E7 peptide ELISA among patients but not among controls. In tests with representative sera, heat denaturation of the translated proteins resulted in a complete loss of reactivity to the E6 protein and a marked decrease in reactivity to the E7 protein. Our study showed that the radioimmunoprecipitation assay discriminates better than the peptide ELISA between patients with invasive cervical cancer and controls and that this is related to the ability of the radioimmunoprecipitation assay to detect conformational epitopes.

Antibodies, Viral↗

PubMedDate not supplied

Analysis of the temporal compressibility of breast tumour marker assays: development of a "near patient" assay.

The aim of this study was to investigate whether immunoassays for circulating MUC1 antigen in breast cancer could be compressed in time so that serum level results would be made available during the time of the patient's visit to clinic. Two assays were used: -The EMCA (Euro DPC) is a liquid phase immunoassay and the ELSA CA15-3 (CIS) is a double determinant solid phase immunoradiometric assay. The effects of shortened incubation times were investigated by assaying standards and unknown samples and comparing the results with those using the standard kit protocols. The binding kinetics of the monoclonal antibodies employed in the assays were analysed separately. We conclude that the EMCA assay can be shortened to 35 min and we have attributed this to the fast binding kinetics inherent in a liquid phase assay. This shortened assay may produce the basis for a useful "near patient" assay. By comparison, the solid phase ELSA CA15-3 assay cannot be compressed without loss in assay performance.

Antibodies, Monoclonal↗

PubMed1988

Comparison of an antimetabolic assay and an antiproliferative assay, both using 3H-thymidine incorporation, to test drug sensitivity of human tumors.

Two assays based on the inhibition of 3H-thymidine incorporation into DNA were used to measure either the antimetabolic or the antiproliferative effects of anticancer drugs. A direct comparison of the two assays was made with cell suspensions obtained from 11 ovarian cancers and 22 malignant melanomas. Drugs with different effects on cell cycle phases were tested by both assays, for a total of 53 drug comparisons. When the sensitivity indices specific for each system was used, a significant association (p less than 0.01) was noted between the two assays. The agreement of both assays in defining in vitro sensitivity or resistance was 100% for ovarian cancer. For melanoma, 97% of samples resistant to the antimetabolic assay were also resistant to the antiproliferative assay; whereas, only 45% of samples sensitive to the antimetabolic assay were sensitive to the antiproliferative assay.

Antimetabolites, Antineoplastic↗

PubMed2005

HLA-B27 typing: evaluation of an allele-specific PCR melting assay and two flow cytometric antigen assays.

BACKGROUND: Human leukocyte antigen B27 (HLA-B27) is a major histocompatibility complex class 1 molecule that is strongly associated with the disease ankylosing spondylitis. Testing for HLA-B27 is of diagnostic value because 90% of patients with ankylosing spondylitis have the B27 antigen. Two commonly used HLA-B27 flow cytometric assays are commercially available. METHODS: An allele-specific polymerase chain reaction (PCR) melting assay for HLA-B27 was compared with two available antigen assays on 371 clinical samples. The accuracy of the assays was measured by receiver operating characteristic analysis using the PCR method and sequencing as the reference standard. RESULTS: When PCR results were compared with those of the antigen assays, complete concordance was observed except for five discrepant results that were resolved by sequence analysis. Using DNA sequencing as the gold standard, the sensitivity and specificity of PCR were 99.6 and 100.0, those of the best single antigen assay were 98.2 and 97.6, and those of a reflex combination of both antigen assays were 98.8 and 97.6. CONCLUSIONS: The allele-specific PCR melting assay for HLA-B27 genotyping is easy to perform and has better sensitivity and specificity than antigen assays. The performance of the two flow cytometric antigen assays depends on the antibody used and the positive cutoff values assigned.

Alleles↗

PubMed1981

Cells involved in the immune response. XXX. An evaluation of the different assays to demonstrate rabbit spleen plaque-forming cells. Enhancement of the assay by anti-target cell antibodies.

Four different procedures for the detection of rabbit spleen plaque-forming cells (PFC) directed toward the sheep erythrocyte (SRBC) antigen were evaluated in terms of their sensitivity. These included the conventional localized hemolysis in gel (LHG) assay, the thin-layer LHG assay, the LH assay using a monolayer of the target SRBC erythrocytes and the localized hemolysis in liquid phase (Cunningham) assay. The latter assay consistently proved to be the most sensitive assay. The sensitivity of this latter assay was further improved by incorporating preformed IgG or IgM antibodies directed toward the target erythrocytes, in subhemolytic concentrations, into the assay. This antibody-enhanced plaque assay in liquid medium is 20-50 times more sensitive than the conventional LHG assay.

Animals↗

PubMed1994

A new rapid and simple non-radioactive assay to monitor and determine the proliferation of lymphocytes: an alternative to [3H]thymidine incorporation assay.

A one-step non-radioactive assay to determine the proliferation of murine lymphocytes, lymphoid tumor cells and hybridoma cells is described. This assay requires the addition of Alamar Blue dye to cell cultures and the degree of change in its color, which is reflective of the extent of cellular proliferation, can be determined by an ELISA plate reader. Alamar Blue must be added during the initial phase of cell culture. The pattern of concanavalin A (ConA) or anti-CD3 antibody-induced proliferative response of murine lymphocytes as assessed by Alamar Blue was similar to that of a [3H]thymidine assay. Similarly, the spontaneous proliferation curve of anti-CD3 antibody secreting cell line (YCD3-1), monocytic macrophage cell lines (PU5-1.8, P388D1, J774.1) and myeloma cells (Sp2/0) as determined by Alamar Blue closely resembled that of the [3H]thymidine assay. The minimum detectable number of proliferating cells was comparable in Alamar Blue and [3H]thymidine assays. Since cell lysis/extraction and washing procedures are not involved in the Alamar Blue assay, this approach has several distinct advantages over currently available assays (eg. [3H]thymidine). First, it allows daily monitoring of proliferation without compromising the sterility of cultures. An indication of proliferation can be evaluated (spectrophotometrically or visually) as early as 24 h after ConA stimulation. Second, unlike previously reported assays, Alamar Blue permits further analysis of proliferating cells by other methods. Analysis of cells in culture with Alamar Blue for various surface antigens (CD44, CD45RB, CD4, heat stable antigen) by flow cytometry revealed that the fluorescent profile and relative percentage of cells in cultures with the Alamar Blue were comparable to those without this reagent. The salient advantages of Alamar Blue assay over the [3H]thymidine assay include: (i) non-radioactivity; (ii) simplicity; (iii) less costly; (iv) non-labor intensive; (v) rapidity of assessment of proliferation of large number of samples; (vi) non-toxicity; (vii) usefulness in determining the kinetics of cell growth of hybridomas; and (viii) non-interference of secretion of antibodies by a hybridoma cell line.

Animals↗

PubMed1995

Comparison of the microgel electrophoresis assay and other assays for genotoxicity in the detection of DNA damage.

Genotoxic agents can be detected by measuring DNA damage which result in the migration of DNA from single cells in agarose, using an electrophoretic field under alkaline conditions. The alkaline microgel electrophoresis technique was compared with in vitro structural chromosomal aberration (SCA) and mutation assays using V79 Chinese hamster lung cells and in vivo assays such as the bone marrow micronucleus assay in mice and a hepatocyte DNA repair assay in rats. Genotoxicants tested were those routinely used as positive control compounds in the various assays. In vitro assays included liver S9 for metabolic activation of cyclophosphamide (CP) for the SCA assay and benzo[a]pyrene (BP) for the mutation assay. A highly significant increase in DNA migration was induced by these agents under circumstances where a significant increase in DNA damage was detected using other endpoints. The alkaline microgel electrophoresis assay thus demonstrated the ability to detect DNA damage coinciding with the induction of DNA damage detected in these other assays for genotoxicity.

Analysis of Variance↗

PubMed1985

Comparison of rat liver foci assay and strain A mouse lung tumor assay to detect carcinogens: a review.

A comparison was performed of the results reported in the literature of chemicals tested in the rat liver foci assay and/or in the strain A lung tumor assay to the results of the chemicals tested in long-term carcinogenicity bioassays. The rat liver foci assay was sensitive to 69% of 54 compounds found to be carcinogenic in long-term bioassays and the strain A lung tumor assay to 54% of 93 carcinogens. None of 10 compounds found to be noncarcinogenic in long-term bioassays were active in the rat liver foci assay, while 7 of 23 noncarcinogens (30%) were active in the lung tumor assay. Ten of the 17 carcinogens negative in the rat liver foci assay are believed to exhibit tumor-promoting activity; 3 are direct-acting alkylating agents (dimethylsulfate, epichlorohydrin, and beta-propiolactone); and the remaining 3 are azobenzene, 1,2-dibromoethane, and thioacetamide. Thirty-two of the 43 carcinogens negative in the lung tumor assay were active in either (1) the mouse liver only, (2) the rat and not in the mouse, or (3) in both the rat and mouse liver but not in other organs of the mouse. It is proposed that additional investigations be undertaken to further evaluate the rat liver foci assay and the strain A mouse lung tumor assay as short-term in vivo tests for the demonstration of the carcinogenic potential of genotoxic (mutagenic) chemicals and environmental samples of complex mixtures.

Adenoma↗

PubMed2000

Evaluation of in vitro reporter gene induction assays for use in a rapid prescreen for compound selection to test specificity in the Tg.AC mouse short-term carcinogenicity assay.

Under ICH guidelines, short-term carcinogenicity assays such as the Tg.AC assay are allowed alternatives for one species in the 2-year rodent bioassay. The Tg.AC transgenic mouse, which carries the v-Ha-ras oncogene under control of the zeta-globin promoter, develops skin papillomas in response to dermal application of carcinogens and tumor promoters. The appropriate specificity of the Tg.AC model for testing pharmaceuticals has not been systematically evaluated. The selection of candidate test compounds among noncarcinogenic pharmaceuticals would be aided by a high-throughput in vitro prescreen correlative of activity in the in vivo Tg.AC assay. Here we describe the development of a prescreen based on correct response to 24 compounds tested previously in Tg.AC mice. The in vitro prescreens, chosen to reflect molecular pathways possibly involved in Tg.AC papilloma formation, consisted of a zeta-globin promoter-luciferase construct stably expressed in K562 cells (Zeta-Luc) and three of the stress-response element-chloramphenicol acetyltransferase (CAT) fusion constructs stably expressed in HepG2 cells that are part of the CAT-Tox (L)iver assay. The stress response elements chosen were the c-fos promoter, the gadd153 promoter, and p53 response element repeats. Of the four assays, the gadd153-CAT assay showed the strongest concordance with activity in the Tg.AC assay, correctly classifying 78% of Tg.AC positive and 83% of Tg.AC negative compounds. The correlation was further improved by adding the Zeta-Luc assay as a second-stage screen. These cell-based assays will be used in a novel approach to selecting candidate compounds that challenge the specificity of the Tg.AC assay toward pharmaceuticals.

Animals↗

PubMed1981

Effect of L-tryptophan on mouse brain 5-hydroxytryptamine: comparison of values obtained using a fluorimetric assay and a liquid Chromatographic assay with electrochemical detection.

5-Hydroxytryptamine (5-HT) in mouse brain and spinal cord was assayed in the same samples using a fluorimetric assay and a high pressure liquid chromatographic (HPLC) assay with electrochemical detection. The HPLC assay was able to detect levels of 5-hydroxytryptamine as low as 0.2-0.5 pmol. With the column (Vydac cation exchange), solvent system (acetate/citrate buffer, 0.1 or 0.2 M, pH 4.8-5.2) extraction procedure and electrode potential (+0.55 V) used, the HPLC assay was specific for 5-HT. When the electrode potential was increased to +0.9 V tryptamine could also be detected, with a longer retention time than 5-hydroxytryptamine. The percent-age increase in mouse brain 5-hydroxytryptamine after pargyline (75 mg/kg) and pargyline L-tryptophan (100 mg/kg) was very similar whether measured by fluorimetry or HPLC, although the fluorimetric assay gave consistently higher absolute values (24-32%) in both control and drug-treated animals. L-Tryptophan (25, 50 and 100 mg/kg) also increased brain 5-hydroxytryptamine with similar percentage increases with either assay method. There was a significant correlation (P less than 0.001) between the values obtained with the two assay methods. The results confirm the use of HPLC with electrochemical detection as a sensitive and specific assay method for 5-hydroxytryptamine and indicate its potential use for the assay of tryptamine, and the importance of determining the electroactivity and retention characteristics of any drugs used.

Animals↗

PubMed1997

Comparison of plasma virus loads among individuals infected with hepatitis C virus (HCV) genotypes 1, 2, and 3 by quantiplex HCV RNA assay versions 1 and 2, Roche Monitor assay, and an in-house limiting dilution method.

The accuracy of different methods for the quantitation of hepatitis C virus in plasma was measured with samples from individuals infected with different genotypes and by using RNA transcripts of predetermined concentrations. Highly reproducible results were observed upon repeat testing of samples by both the original version of the Chiron branched-DNA (bDNA) assay (Quantiplex RNA assay; bDNA-1) and the currently available version (Quantiplex HCV RNA 2.0 assay; bDNA-2). A greater variability was observed in the Roche Monitor assay (correlation coefficient of 0.537, compared with 0.942 and 0.964 for the bDNA-1 and bDNA-2 assays, respectively). Significant differences in the efficiency of detection of genotypes 1, 2, and 3 were observed for the bDNA-1 and Roche Monitor assays, whereas the bDNA-2 assay and nested PCR at limiting dilution were able to quantify genotypes with equal sensitivity. By quantifying RNA transcripts of different genotypes, the sensitivities of the Roche Monitor assay for sequences of the type 2 and type 3 transcripts were estimated to be 11 and 8% of those achieved for genotype 1. When correction factors based upon these results and those from quantitation of circulating viral RNA sequences in samples from blood donors were used, the genotype-specific differences in virus load in samples from blood donors were no longer observed, consistent with previous studies with corrected values from the bDNA-1 assay. These results suggest that many of the previous studies evaluating the effect of genotype and virus load on the response to interferon using methods such as the Roche Monitor assay and other competitive PCR methods require reinterpretation. Differences in efficiency of quantitation should be taken into account in future investigations of the relationship between genotype and virus load.

Genes, Viral↗

PubMed1999

Evaluation of a bacteriophage-based assay (phage amplified biologically assay) as a rapid screen for resistance to isoniazid, ethambutol, streptomycin, pyrazinamide, and ciprofloxacin among clinical isolates of Mycobacterium tuberculosis.

Rapid molecular assays for the detection of mutations associated with rifampin resistance in Mycobacterium tuberculosis are commercially available. However, they are complex and expensive and have predictive values of 90 to 95%. Molecular assays for other drugs are less predictive of resistance. Ideally, assays based on phenotypic markers should be used for susceptibility testing, but these can take weeks to complete. We previously described a rapid phenotypic assay, the phage amplified biologically (PhaB) assay, for the rapid determination of rifampin and isoniazid susceptibility in clinical isolates of M. tuberculosis. In this study, we extended the assay to the study of ethambutol, pyrazinamide, streptomycin, and ciprofloxacin. After the optimization of antibiotic concentrations and incubation conditions, the assay was applied to each drug for a total of 157 isolates. The correlations between the results of the PhaB assay and the resistance ratio method were 94% for isoniazid, 96% for streptomycin, 100% for ciprofloxacin, 88% for ethambutol, and 87% for pyrazinamide. For ciprofloxacin, ethambutol, and pyrazinamide, significantly better correlations were found when a 90% reduction in plaque count was used as the cutoff. Turnaround times for the PhaB assay were 2 to 3 days, compared with 10 days for the resistance ratio method. We believe that this low-cost assay may have widespread applicability for the rapid screening of drug resistance in M. tuberculosis isolates, especially in developing countries.

Antitubercular Agents↗