Evaluation of HIV ELISA diagnostic kit developed at the Institute of Primate Research, Nairobi, Kenya

The first diagnostic kits utilizing the enzyme-linked immunosorbent assay (ELISA) technique were developed in mid-eighties, and since then, this technique has become an increasingly important tool for screening multiple samples of blood or serum for presence of antibodies to various infectious pathogens, especially human immunodeficiency virus (HIV) in blood banks. However, most of the commercial diagnostic kits currently available in the market are too expensive, hence not easily affordable in most Diagnostic Laboratories. We designed an ELISA kit for diagnosis of HIV and compared it with some of the commercial kits. We used blood samples from the blood bank at the National Public Health Laboratory Services (NPHLS) in Nairobi and from patients referred to the Kenya Medical Research Institute (KEMRI) for HIV screening. Two commercial kits were used, Wellcozyme HIV Recombinant kit and Recombigen (env & gag) HIV-1 EIA kit. Out of 1350 samples tested by Recombigen (env & gag) HIV-1 EIA kit, 419 (31.0% ) were positive while 421 (31.2% ) samples were positive by Wellcozyme HIV Recombinant kit. Our ELISA kit detected a total of 431 positive samples out of 1350 (31.9% ), which was almost identical to the results from the other kits. Our kit was nearly identical in terms of sensitivity and specificity to the other two commercial kits used in this study. Thus our ELISA system, which is much cheaper than the commercial kits currently available in the market, offers a more affordable system for routine HIV tests.     

Evaluation of a simultaneous HIV antigen and antibody detection test in Korean population

Current diagnosis of human immunodeficiency virus (HIV) infection relies on the detection of anti-HIV antibodies by enzyme-linked immunosorbent assay (ELISA). Recently, kits detecting both p24 antigenemia and anti-HIV/anti-HIV2 antibodies have been developed. Thus, it is necessary to compare those kits developed as such. The aim of this study was to evaluate the diagnostic efficiency of a simultaneous detection test of p24 antigen and anti-HIV1/2 antibodies in a low prevalence area. Eight hundred and four randomly selected sera proven negative for HIV infection and 110 sera from 54 patients diagnosed as HIV infected, obtained between 1999 and 2000, were used for this study. One commercial lot of panels composed of consecutive sera obtained from known HIV-infected patient was included. Anti-HIV1/2 antibodies were detected by two different commercial ELISA kits, one from Korean and the other from German manufacturer. P24 antigen test was performed by ELISA. The simultaneous HIV antigen and antibody detection test was carried out. In the meantime, HIV RNA PCR and anti-HIV and anti-HIV2 western blot assays were also performed to confirm the test results in cases the test results didn't agree. The simultaneous detection kit showed 100% sensitivity and 99.6% specificity. Furthermore, the test displayed the possibility of earlier diagnosis than conventional anti-HIV1/2 ELISA with the results obtained from a group of consecutive panel sera infected with HIV. From these results, we concluded that the simultaneous HIV antigen and antibody detection test can be applied as a substitute clinical screening test in the place of conventional anti-HIV1/2 ELISA, and there is the probable benefit of early diagnosis.     

Comparison of five commercial western blot kits for detection of human immunodeficiency virus 1

Twenty-two human immunodeficiency virus 1 (HIV-1) enzyme immunoassay (EIA) reactive and two non-reactive patient specimens were analyzed using five commercially available HIV-1 Western blot kits. The percentage of HIV-1 bands detected by each kit was recorded. The differences between pairs of kits were not found to be statistically significant at the 0.05 level. All EIA reactive specimens were reconfirmed as reactive by each Western blot kit tested.     

Comparison of commercial kits for detection of cryptococcal antigen.

Although kits to detect cryptococcal antigen are used widely to diagnose cryptococcal infection, the comparative performance of commercially available assays has not been evaluated in the past decade. Therefore, we compared the sensitives and specificities of five commercially available kits for detecting cryptococcal antigen (four latex agglutination test kits--Calas [Meridian Diagnostics])--Crypto-LA [International Biological Labs], Myco-Immune [MicroScan], and Immy [Immunomycologics]--and an enzyme immunoassay kit, Premier [Meridian Diagnostics]) with culture for the diagnosis of cryptococcal meningitis and fungemia. Of 182 cerebrospinal fluid (CSF) and 90 serum samples submitted for cryptococcal antigen and fungal culture, 49 (19 and 30 samples, respectively) from 20 patients had a culture positive for Cryptococcus neoformans. For CSF specimens, the sensitivities and specificities of all kits were comparable (sensitivity, 93 to 100%; specificity, 93 to 98%). There was a significant difference in sensitivities of the kits when serum samples were tested with the International Biological Labs and MicroScan kits, which do not pretreat serum with pronase. These kits were less sensitive (sensitivity, 83%) than the Immy and Meridian latex kits (sensitivity, 97%), which do pretreat with pronase. The sensitivity of the Meridian enzyme immunoassay kit was comparable to that of the pronase-containing latex kits. These kits were of equivalent specificities (93 to 100%) when testing serum. Some of the currently available kits have limitations that need to be recognized for proper interpretation of results. Specifically, the use of pronase on serum samples reduces the number of false-positive results, and a titer of < or = 1:4 can be a false-positive result when CSF samples are being tested.     

Anti-HIV positivity in Thailand: the usefulness of another ELISA test kit and Western blot as confirmatory tests

Sera from 47 individuals repeatedly reactive in one screening ELISA system (designated as ELISA-A) for antibodies against human immunodeficiency virus (HIV) were evaluated by a second ELISA system (designated as ELISA-B) as well as by the Western blot technique. Both ELISA systems and the Western blot were positive in all of the 14 patients with clinical diagnoses of AIDS and AIDS-related persistent generalized lymphadenopathy (PGL). Of the 7 asymptomatic gays whose sera were repeatedly reactive in ELISA-A, 5 were also reactive in ELISA-B and these were the ones with positive Western blot tests. Eight and 17 ELISA-A reactive individuals were uncovered during a survey of 2,699 female prostitutes and 15,210 potential workers for Saudi Arabia respectively. All of these 25 individuals were ELISA-B and Western blot negative, an indication of false-positive reactivity with ELISA-A. Our studies indicate that the prevalence of HIV infection among the general Thai population is still low, and that the specificity of two ELISA test kits for anti-HIV may differ considerably. We concluded that evaluation of test kits should include studies in tropical countries where ecological conditions, climate and background endemic disease patterns are different than in the countries producing the diagnostic systems. Such studies are needed to identify the most sensitive and specific kits for worldwide application. We did discover that concordant positivity of two different ELISA test kits served as a reliable and inexpensive confirmatory test for anti-HIV.     

Evaluation and diagnostic usefulness of domestic and imported enzyme-linked immunosorbent assays for detection of human immunodeficiency virus type 1 antibody in India

Diagnosis of human immunodeficiency virus (HIV) infection is important for patient management and prevention of new infections. The number of test kits available for the detection of HIV antibodies is unprecedented. In order to identify appropriate test kits, we evaluated a variety of commercial kits manufactured abroad as well as in India. The plasma and serum specimens (n=264) were collected from individuals attending the Voluntary Counseling and Testing Centre at the YRG Centre for AIDS and Education. The specimens were used to evaluate six commercially available HIV test kits: Enzaids HIV 1+2, HIV-CheX, Murex HIV-1.2.0, Genscreen HIV 1/2 version 2, Vironostika HIV Uni-Form II Ag/Ab, and CombAids RS Advantage. High sensitivities and specificities (>or=99%) were observed for the Enzaids, Murex, Vironostika, and CombAids assays. HIV-CheX showed the highest number of false-positive and false-negative results. The Genscreen test also gave many false positives. The study indicated that the Enzaids, Murex, and Vironostika enzyme-linked immunosorbent assay kits and the CombAids RS Advantage rapid assay could be used to achieve acceptable results for the detection of HIV antibodies. A combination of two tests is recommended to optimize the efficiency of HIV antibody testing algorithms, especially when evaluation with an HIV Western blot confirmatory test is not possible.     

Efficiency of two commercial kits in serodiagnosis of leptospiral uveitis

Purpose: Uveitis is an important complication of systemic leptospirosis that can occur months to years after systemic infection. The gold standard technique Microscopic Agglutination Test (MAT) is less sensitive and more complicated. All the commercial kits currently available are for early detection of acute systemic leptospiral infection. The purpose of this study is to evaluate the efficiency of two commercial kits in serodiagnosis of leptospiral uveitis, which is a late manifestation. Materials and Methods: Serum samples from leptospiral uveitis patients 20 MAT positive, 20 MAT negative, 15 non-leptospiral uveitis patients, 20 systemic leptospiral infected patients and 21 controls were selected. These samples were tested for the presence of leptospiral IgM antibodies by (i) MAT using a panel of 20 serovars, (ii) LEPTO IgM MICROLISA (J.Mitra & Co.Pvt. Ltd, India) and (iii) Leptocheck (Zephyr Biomedicals, India). The statistical analysis was carried out using stata 11.0. Results: Total of 96 samples were tested with two commercial kits, Lepto IgM MICROLISA and Leptocheck. The sensitivity and specificity of Lepto IgM MICROLISA was 60% and 55% and Leptocheck was 80% and 59% respectively in comparison to MAT. In comparison to clinical diagnosis the sensitivity of IgM Microlisa was 55%, Leptocheck 70% and specificity of IgM MICROLISA was 58.33% and leptocheck was 69.44%. Conclusion: Commercial kits though sensitive and specific for systemic leptospirosis, have limited diagnostic capacity for leptospiral uveitis. Therefore it is essential to develop an inhouse serodiagnostic method specific for leptospiral uveitis patients using local leptospiral isolates.     

Evaluation and Diagnostic Usefulness of Domestic and Imported Enzyme-Linked Immunosorbent Assays for Detection of Human Immunodeficiency Virus Type 1 Antibody in India

Diagnosis of human immunodeficiency virus (HIV) infection is important for patient management and prevention of new infections. The number of test kits available for the detection of HIV antibodies is unprecedented. In order to identify appropriate test kits, we evaluated a variety of commercial kits manufactured abroad as well as in India. The plasma and serum specimens (n = 264) were collected from individuals attending the Voluntary Counseling and Testing Centre at the YRG Centre for AIDS and Education. The specimens were used to evaluate six commercially available HIV test kits: Enzaids HIV 1+2, HIV-CheX, Murex HIV-1.2.0, Genscreen HIV 1/2 version 2, Vironostika HIV Uni-Form II Ag/Ab, and CombAids RS Advantage. High sensitivities and specificities (≥99%) were observed for the Enzaids, Murex, Vironostika, and CombAids assays. HIV-CheX showed the highest number of false-positive and false-negative results. The Genscreen test also gave many false positives. The study indicated that the Enzaids, Murex, and Vironostika enzyme-linked immunosorbent assay kits and the CombAids RS Advantage rapid assay could be used to achieve acceptable results for the detection of HIV antibodies. A combination of two tests is recommended to optimize the efficiency of HIV antibody testing algorithms, especially when evaluation with an HIV Western blot confirmatory test is not possible.     

FDA approves two new approaches to HIV testing. Food and Drug Administration

The Food and Drug Administration (FDA) approved two HIV home testing kits. Johnson & Johnson's Confide kit, currently only available in Texas and Florida, costs about $40. It includes a lancet to draw blood, a self-addressed postage-paid envelope to mail the sample, and a 14-digit anonymous identification code. Epitope has developed a kit called OraSure, which uses saliva samples to measure HIV antibodies. Persons testing positive will be connected directly with a trained counselor, selected from the National AIDS Hotline database. The Centers for Disease Control and Prevention (CDC) estimate that as many as two-thirds of the people at risk have not been tested for HIV, and 42 percent of those would be likely to use a home collection kit which provides anonymity.     

Evaluation of two commercial human T-cell lymphotropic virus western blot (immunoblot) kits with problem specimens.

We evaluated two commercial human T-cell lymphotropic virus (HTLV) Western blot (WB; immunoblot) kits, Cambridge Biotech Corp. (CBC) and Diagnostic Biotechnology Ltd. (DBL). Both methods employ HTLV type I (HTLV-I) viral lysate and rgp21. The DBL WB kit also distinguishes between HTLV-I and HTLV-II antibodies, using an HTLV-I-specific and an HTLV-II-specific recombinant. Fifty weakly reactive HTLV-II-positive plasma specimens which were falsely negative with the Abbott enzyme immunoassay (EIA) and 50 Ortho EIA false-positive samples were selected to determine sensitivity and specificity. The sensitivities of the CBC and the DBL WB kits were 90 and 68%, respectively. All positive samples reacted with rgp21 in both kits, but some did not display core bands. Five samples were typed as HTLV-I and four were typed as dual infection by the DBL WB kit. The specificities of the CBC and DBL kits were 48 and 70%, respectively. The most prevalent WB reaction with the negative samples was with the core protein, p19, followed by p24 and p28 for CBC and rgp21 and p28 for DBL. DBL had two false-positive interpretations, and CBC had none, rgp21 was the most sensitive antigen in both kits for the weakly reactive HTLV-II samples. If all samples not reacting with this protein were interpreted as WB negative, regardless of other bands, the specificity would improve to 90% for CBC and 86% for DBL.     

Comparison of six commercial DNA extraction kits for recovery of cytomegalovirus DNA from spiked human specimens

We evaluated six commercially available DNA extraction kits for their ability to recover DNA from various dilutions of cytomegalovirus (CMV) added to four different specimens: bronchoalveolar lavage, cerebral spinal fluid, plasma, and whole blood. The kits evaluated included the Puregene DNA isolation kit (PG), Generation Capture Column kit, MasterPure DNA purification kit, IsoQuick nucleic acid extraction kit, QIAamp blood kit, and NucliSens isolation kit (NS). All six kits evaluated effectively removed PCR inhibitors from each of the four specimen types and produced consistently positive results down to a spiked concentration of 200 PFU of whole CMV per ml. However, the NS and PG resulted in the most consistently positive results at the lowest concentrations of spiked CMV (4 and 0.4 PFU/ml) and, in this evaluation, offered the most sensitive methods for extracting CMV DNA from the four different spiked specimens. Processing time and cost were also evaluated.     

Comparison of two commercial microimmunofluorescence kits and an enzyme immunoassay kit for detection of serum immunoglobulin G antibodies to Chlamydia pneumoniae

We compared the MRL and the Labsystems Chlamydia pneumoniae microimmunofluorescence (MIF) immunoglobulin G (IgG) kits and the Labsystems enzyme immunoassay (EIA) kit in a blinded study of 83 serum samples in which we evaluated titers, cross-reactivity to other species, and reproducibility. There was no statistically significant difference between the MRL and the Labsystems MIF kits in the endpoint titers of IgG antibody to C. pneumoniae. The correlation between the results obtained with these two MIF kits was excellent (r = 0.95; P = 0.001). The cross-reactivity of the C. pneumoniae-positive sera with C. trachomatis- and C. psittaci-positive sera was assessed for each MIF kit. For C. pneumoniae-positive sera with titers of > or =32, the Labsystems MIF kit exhibited more cross-reactivity to C. psittaci than the MRL kit did. The values obtained with the Labsystems EIA kit represented single dilutions of serum specimens expressed as enzymeimmuno units on a continuous scale. The results obtained with the Labsystems EIA kit correlated moderately well with those obtained with each MIF kit when they were compared for their abilities to detect IgG antibodies to C. pneumoniae (for the MRL MIF kit, r = 0.79 [P = 0.001]; for the Labsystems MIF kit, r = 0.78 [P = 0.001]). The results obtained with the commercial MRL and Labsystems MIF kits and the Labsystems EIA kit tested were reproducible; and the kits were standardized, had quality control reagents, and are suitable for detection of C. pneumoniae antibodies in serum and for use in interlaboratory studies. Validation of the use of these kits for clinical diagnosis still needs further evaluation.     

Utility of various commercially available human immunodeficiency virus (HIV) antibody diagnostic kits for use in conjunction with efficacy trials of HIV-1 vaccines.

There is a need for human immunodeficiency virus (HIV) screening assays which will distinguish uninfected HIV vaccine recipients from HIV-infected individuals. Commercial screening kits were used to test serum samples from low- and high-risk participants in clinical trials before and after immunization with various recombinant HIV type 1 (HIV-1) envelope glycoprotein 120 (gp120) candidate vaccines. All kits were 100% sensitive in detecting HIV infection. Both Murex Single Use Diagnostic System and United Biomedical, Inc., HIV type 1 or 2 (HIV-1/2) enzyme immunoassay (EIA) kits, which detect antibodies to HIV-1 gp41, were 98 to 100% specific when used to screen baseline or recombinant gp120-vaccinated populations as vaccine-induced antibodies to gp120 were nonreactive in these tests. The Abbott HIVAB HIV-1 EIA (lysate of whole infected cells, reactive with anti-gp120 antibodies) gave high levels of reactivity due to vaccine-induced antibodies and a high baseline rate of false positives (12 of 83) among nonvaccinated high-risk volunteers. Assays containing only gp41 and p24 solid-phase components are compatible with gp120-based vaccines but are unlikely to be useful in a similar role for vaccines containing gp160, gp41, or gp120 plus p24 antigens. Efficacy trials must be designed in concert with available diagnostic screening assays to avoid problems caused by vaccine-induced seroconversion in high-risk populations.     

Evaluation of a new Staphylococcus aureus latex agglutination kit, Prolex Staph Xtra, against other third-generation kits

Staphylococcus aureus, including methicillin-resistant strains, continues to be a common cause of infection/colonisation, which necessitates accurate and prompt diagnosis in the laboratory. Several rapid agglutination tests that aid this function are available, and some have been modified to improve their performance. One such kit, Prolex Staph Xtra, has been released recently. This study aims to compare this kit with other improved kits (i.e., Pastorex Staph-Plus, Staphaurex Plus and Staphytect Plus) and investigate their ability to confirm the identity of 100 strains of S. aureus. Results showed that 50 were resistant to methicillin. Specificity was checked against 30 strains of coagulase-negative staphylococci and 20 Enterococcus species isolates. Of the four kits tested, Prolex Staph Xtra and Pastorex Staph-Plus proved superior in terms of sensitivity and speed.     

Multicenter evaluation of use of dried blood and plasma spot specimens in quantitative assays for human immunodeficiency virus RNA: measurement,precision, and RNA stability

Eleven laboratories evaluated the use of dried blood and plasma spots for quantitation of human immunodeficiency virus (HIV) RNA by two commercially available RNA assays, the Roche Amplicor HIV-1 Monitor and the bioMerieux NucliSens HIV-1 QT assays. The recovery of HIV RNA was linear over a dynamic range extending from 4,000 to 500,000 HIV type 1 RNA copies/ml. The Monitor assay appeared to have a broader dynamic range and seemed more sensitive at lower concentrations. However, the NucliSens assay gave more consistent results and could be performed without modification of the kit. HIV RNA was stable in dried whole blood or plasma stored at room temperature or at -70 degrees C for up to 1 year. Dried blood and dried plasma spots can be used as an easy and inexpensive means for the collection and storage of specimens under field conditions for the diagnosis of HIV infection and the monitoring of antiretroviral therapy.     

Multisite comparison of high-sensitivity multiplex cytokine assays

The concentrations of cytokines in human serum and plasma can provide valuable information about in vivo immune status, but low concentrations often require high-sensitivity assays to permit detection. The recent development of multiplex assays, which can measure multiple cytokines in one small sample, holds great promise, especially for studies in which limited volumes of stored serum or plasma are available. Four high-sensitivity cytokine multiplex assays on a Luminex (Bio-Rad, BioSource, Linco) or electrochemiluminescence (Meso Scale Discovery) platform were evaluated for their ability to detect circulating concentrations of 13 cytokines, as well as for laboratory and lot variability. Assays were performed in six different laboratories utilizing archived serum from HIV-uninfected and -infected subjects from the Multicenter AIDS Cohort Study (MACS) and the Women's Interagency HIV Study (WIHS) and commercial plasma samples spanning initial HIV viremia. In a majority of serum samples, interleukin-6 (IL-6), IL-8, IL-10, and tumor necrosis factor alpha were detectable with at least three kits, while IL-1β was clearly detected with only one kit. No single multiplex panel detected all cytokines, and there were highly significant differences (P < 0.001) between laboratories and/or lots with all kits. Nevertheless, the kits generally detected similar patterns of cytokine perturbation during primary HIV viremia. This multisite comparison suggests that current multiplex assays vary in their ability to measure serum and/or plasma concentrations of cytokines and may not be sufficiently reproducible for repeated determinations over a long-term study or in multiple laboratories but may be useful for longitudinal studies in which relative, rather than absolute, changes in cytokines are important.     

Advantage of using a home-made ELISA kit for detection of Helicobacter pylori infection over commercially imported kits

PURPOSE: To evaluate a home-made ELISA kit for detection of Helicobacter pylori (Hp) infection and comparison of its immunologic criteria with those of foreign commercial kits. METHODS: A home-made IgG ELISA kit was developed using soluble antigenic fractions of Hp proteins. Confirmed sera were tested and serological criteria were evaluated through assessment of 199 serum samples. RESULTS: The accuracy, sensitivity and specificity values of home-made kit were 92, 92 and 90.4%, respectively. These immunologic criteria for Trinity kit were 95.2, 95.2 and 95% in comparison with IBL kit (91.3, 92.2 and 88.5%), BIOHIT kit (72.4, 41.6 and 94.1%) and HelicoBlot2.1 (94.2, 93.4 and 100%). Kappa agreement assessment demonstrated that two of the imported ELISA kits had fair to moderate agreement with the home-made kit while the other one had a poor agreement value. CONCLUSIONS: Apart from comparable values between the home-made kit and the most efficient imported kit (Trinity) there was significant cost benefit. Therefore, we recommend the home-made kit as a suitable substitution for detection of Hp infection in the Iranian population.     

Clinical evaluation of the signal-to-cutoff ratios of hepatitis C virus antibody screening tests used in China

The clinical diagnosis of hepatitis C virus (HCV) infection is important to direct an accurate course of therapy. Previous studies have reported a correlation between the signal-to-cutoff (S/CO) ratios of the anti-HCV screening test and confirm HCV infections for American anti-HCV screening kits as well as for those in China. It is currently unknown whether clinical laboratories use the same threshold S/CO ratios under routine conditions and if these values are acceptable for the analysis of Chinese samples. A total of 336 anti-HCV screening-test-positive serum samples were tested in duplicate using different lots of three most commonly used enzyme immunoassay (EIA) kits available in China. Samples were also tested using the Architect Anti-HCV chemiluminescent microparticle immunoassay (CMIA) kit and measured for HCV RNA. Recombinant immunoblot assays (RIBA) were additionally performed on samples with HCV RNA-negative results with RIBA HCV 3.0. The relationship between S/CO ratios and confirmed HCV infection rates were analyzed. The threshold S/CO ratio for each screening kit correlated with the ≥ 95% positive predictive value was InTec 12.0, KHB 4.0, Wantai 5.0, and Abbott Architect 5.0. Therefore, the same threshold S/CO ratios for manufactured domestically EIA kits was difficult to attain. A multi-center study with a large sample size is required to identify a uniform threshold S/CO ratio for use in different diagnostic laboratories. Alternatively, individual laboratories may be required to establish threshold S/CO ratios in their own laboratories to obtain consistent diagnostic results.     

Detection of Chlamydia trachomatis with fluorescent monoclonal antibody

Commercial kits of fluorescein-labelled monoclonal antibody against Chlamydia trachomatis have been evaluated (1) as an alternative to Giemsa staining for detection of chlamydia inclusions in cell culture and (2) for direct detection of chlamydia in conjunctival, urethral and cervical smears. The inclusion-detection kit (Micro Trak Culture Confirmation Test) was tested on 270 cultures and was found to be highly sensitive, detecting all 16 Giemsa-positive specimens plus an additional 3 that were negative by Giemsa. It was also superior to Giemsa-staining in terms of simplicity of use, ease of detection, and readability with toxic specimens. The direct detection kit (Micro Trak Direct Specimen Test) gave results which agreed with the culture result for all 33 genital tract specimens and for 32 of 34 conjunctival specimens tested in parallel. The kit is considered to be a valuable test for diagnosis of chlamydial infection by laboratories lacking adequate tissue-culture facilities.     

Comparative study of the diagnostic contribution of C-terminal and medio-regional determination of parathyroid hormone in man

In this study, we compared serum parathyrin radioimmunoassay values obtained with three commercially available kits in a series of normal subjects, patients on dialysis, patients with primary hyperparathyroidism and with hypercalcemia due to malignancy. The calcium of these subjects was simultaneously evaluated. Two of these three kits measure two different C-terminal portions of the molecule and the third the mid region of PTH. The Behring and Byk kits were most efficient in that the results were obtained rapidly. The mid region assay is not more contributive than the C-terminal assays. Among these, the Behringer kit seems to produce the best diagnostic discrimination when the PTH and calcium are coupled. As far as the diagnostic specificity is considered, the latter kit seems however less efficient than the two others.