- Email: [email protected]
Response to the Letter to the Editor by Prof. Viroj Wiwanitkit
Preventive Veterinary Medicine 119 (2015) 91–92
Contents lists available at ScienceDirect
Preventive Veterinary Medicine journal homepage: www.elsevier.com/locate/prevetmed
Reply to Letter to the Editor Response to the Letter to the Editor by Prof. Viroj Wiwanitkit Dear Editor, I thank the appreciation by Prof. Wiwanitkit about the interest of our research. In reference to the comments, I am afraid that I must disagree. The first study that is cited (Henning and Sting, 2002) says that the ELISA test “seems to be a very sensitive assay for the detection of Coxiella burnetii but it has a lack in specificity”. The authors also mentioned that is an adequate test for “large scales of samples”, and I think that our study, with 2668 samples, is included in this group. In reference to the second study cited (Field et al., 2002, not 2012), it is clearly contradictory with the first one, because the authors mentioned a great specificity (96%) but a medium-low sensitivity (71%). In addition, although the study by Field et al. (2002) is used to argue that “false positive can be seen in several infections such as leptospirosis and legionellosis”, only in 1/213 animals was detected cross-reactivity with Legionella and in another 1/213 cross-reactivity with Leptospira. I think it is not a severe problem. In fact, the study also reports that no cross reactivity was detected with Mycoplasma, Brucella, and Chlamydia infections, so I cannot understand why it is said that false positive are a problem based in a study where 96% of specificity is detected. We have not data about Legionella, but we have it data about Leptospira infection (data still not published). We calculated the Kappa statistic between both seropositivities and its value was 0.089, so we do not feel that cross reactivity with Leptospira is a problem in our study. Summarizing, two studies with opposite results were used, but any of these have studied the IDEXX Q fever test, so I think the results are not applicable to our study. The manufacturer specify about this test: “The IDEXX Q Fever Ab Test, available from IDEXX Laboratories, has shown excellent specificity and high sensitivity consistently competitive with the complement fixation test”. The sensitivity and specificity of this ELISA test (100% and 97.8%, respectively) have been supplied by the manufacturer. This test has been authorized by the European Union it has been authorized and used by the US government (https://www.fbo.gov/index?s=opportunity&mode=form& id=2db373d02e2d4c8a50c13e0ec587c9e0&tab=core& cview=0) and it has been used in studies published around
http://dx.doi.org/10.1016/j.prevetmed.2015.02.007 0167-5877/© 2015 Elsevier B.V. All rights reserved.
the world (Agger et al., 2010, 2013; Khalili et al., 2011; Vongxay et al., 2012) The third study mentioned (Majidzadeh et al., 2014) only says that the cutoff >1:1024 is not recommended because the increased false-negative findings, but this study is about PCR and it even no mention ELISA technique, so I cannot understand why it is mentioned as an argument to discuss our study. Finally, I agree that immuno PCR described by Malou et al. (2012) is a good technique, but it is adequate for diagnose and not for epidemiological studies. In fact, several seropositive animals would result negative to PCR because they would have eliminate the bacteria. In addition, the cost of analyze 2668 samples with PCR or immune PCR would be very difficult (almost impossible) to be assumed. As conclusion, I think that our study has been adequately performed. In my opinion, the arguments by Prof. Wiwanitkit are not correct and they are poorly based. The ELISA test remains nowadays as the best technique (in fact it is the most used test) for large epidemiological studies and I could not find reasons why the ELISA test by IDEXX would be a bad kit to detect antibodies against C. burnetii infection. Sincerely: Prof. Alfonso Carbonero Martínez References Agger, J.F., Christoffersen, A.B., Rattenborg, E., Nielsen, J., Agerholm, J.S., 2010. Prevalence of Coxiella burnetii antibodies in Danish dairy herds. Acta Vet. Scand. 52, 5. Agger, J.F., Paul, S., Christoffersen, A.B., Agerholm, J.S., 2013. Risk factors for Coxiella burnetii antibodies in bulk tank milk from Danish dairy herds. Acta Vet. Scand. 55, 80. Field, P.R., Santiago, A., Chan, S.W., Patel, D.B., Dickeson, D., Mitchell, J.L., Devine, P.L., Murphy, A.M., 2002. Evaluation of a novel commercial enzyme-linked immunosorbent assay detecting Coxiella burnetiispecific immunoglobulin G for Q fever prevaccination screening and diagnosis. J. Clin. Microbiol. 40, 3526–3529. Henning, K., Sting, R., 2002. Definitive ability of stamp-staining, antigenELISA, PCR and cell culture for the detection of Coxiella burnetii. Berl. Munch. Tierarztl. Wochenschr. 115, 381–384. Khalili, M., Sakhaee, E., Aflatoonian, M.R., Shahabi-Nejad, N., 2011. Herdprevalence of Coxiella burnetii (Q fever) antibodies in dairy cattle farms based on bulk tank milk analysis. Asian Pac. J. Trop. Med. 4, 58–60. Majidzadeh, K., Mohseni, A., Soleimani, M., 2014. Construction and evaluation of a novel internal positive control (IPC) for detection of Coxiella burnetii by PCR. Jundishapur J. Microbiol. 7, e8849. Malou, N., Renvoise, A., Nappez, C., Raoult, D., 2012. Immuno-PCR for the early serological diagnosis of acute infectious diseases: the Q fever paradigm. Eur. J. Clin. Microbiol. Infect. Dis. 31, 1951– 1960.
92
Reply to Letter to the Editor / Preventive Veterinary Medicine 119 (2015) 91–92 ∗ Tel.:
Vongxay, K., Conlan, J.V., Khounsy, S., Dorny, P., Fenwick, S., Thompson, R.C., Blacksell, S.D., 2012. Seroprevalence of major bovine-associated zoonotic infectious diseases in the Lao People’s Democratic Republic. Vector Borne Zoonotic Dis. 12, 861–866.
+34 957 21 87 25; fax: +34 957 21 87 25. E-mail address: [email protected]
Alfonso Carbonero ∗ Department of Animal Health, Veterinary Faculty, University of Cordoba, Córdoba 14006, Spain
6 February 2015
Contents lists available at ScienceDirect
Preventive Veterinary Medicine journal homepage: www.elsevier.com/locate/prevetmed
Reply to Letter to the Editor Response to the Letter to the Editor by Prof. Viroj Wiwanitkit Dear Editor, I thank the appreciation by Prof. Wiwanitkit about the interest of our research. In reference to the comments, I am afraid that I must disagree. The first study that is cited (Henning and Sting, 2002) says that the ELISA test “seems to be a very sensitive assay for the detection of Coxiella burnetii but it has a lack in specificity”. The authors also mentioned that is an adequate test for “large scales of samples”, and I think that our study, with 2668 samples, is included in this group. In reference to the second study cited (Field et al., 2002, not 2012), it is clearly contradictory with the first one, because the authors mentioned a great specificity (96%) but a medium-low sensitivity (71%). In addition, although the study by Field et al. (2002) is used to argue that “false positive can be seen in several infections such as leptospirosis and legionellosis”, only in 1/213 animals was detected cross-reactivity with Legionella and in another 1/213 cross-reactivity with Leptospira. I think it is not a severe problem. In fact, the study also reports that no cross reactivity was detected with Mycoplasma, Brucella, and Chlamydia infections, so I cannot understand why it is said that false positive are a problem based in a study where 96% of specificity is detected. We have not data about Legionella, but we have it data about Leptospira infection (data still not published). We calculated the Kappa statistic between both seropositivities and its value was 0.089, so we do not feel that cross reactivity with Leptospira is a problem in our study. Summarizing, two studies with opposite results were used, but any of these have studied the IDEXX Q fever test, so I think the results are not applicable to our study. The manufacturer specify about this test: “The IDEXX Q Fever Ab Test, available from IDEXX Laboratories, has shown excellent specificity and high sensitivity consistently competitive with the complement fixation test”. The sensitivity and specificity of this ELISA test (100% and 97.8%, respectively) have been supplied by the manufacturer. This test has been authorized by the European Union it has been authorized and used by the US government (https://www.fbo.gov/index?s=opportunity&mode=form& id=2db373d02e2d4c8a50c13e0ec587c9e0&tab=core& cview=0) and it has been used in studies published around
http://dx.doi.org/10.1016/j.prevetmed.2015.02.007 0167-5877/© 2015 Elsevier B.V. All rights reserved.
the world (Agger et al., 2010, 2013; Khalili et al., 2011; Vongxay et al., 2012) The third study mentioned (Majidzadeh et al., 2014) only says that the cutoff >1:1024 is not recommended because the increased false-negative findings, but this study is about PCR and it even no mention ELISA technique, so I cannot understand why it is mentioned as an argument to discuss our study. Finally, I agree that immuno PCR described by Malou et al. (2012) is a good technique, but it is adequate for diagnose and not for epidemiological studies. In fact, several seropositive animals would result negative to PCR because they would have eliminate the bacteria. In addition, the cost of analyze 2668 samples with PCR or immune PCR would be very difficult (almost impossible) to be assumed. As conclusion, I think that our study has been adequately performed. In my opinion, the arguments by Prof. Wiwanitkit are not correct and they are poorly based. The ELISA test remains nowadays as the best technique (in fact it is the most used test) for large epidemiological studies and I could not find reasons why the ELISA test by IDEXX would be a bad kit to detect antibodies against C. burnetii infection. Sincerely: Prof. Alfonso Carbonero Martínez References Agger, J.F., Christoffersen, A.B., Rattenborg, E., Nielsen, J., Agerholm, J.S., 2010. Prevalence of Coxiella burnetii antibodies in Danish dairy herds. Acta Vet. Scand. 52, 5. Agger, J.F., Paul, S., Christoffersen, A.B., Agerholm, J.S., 2013. Risk factors for Coxiella burnetii antibodies in bulk tank milk from Danish dairy herds. Acta Vet. Scand. 55, 80. Field, P.R., Santiago, A., Chan, S.W., Patel, D.B., Dickeson, D., Mitchell, J.L., Devine, P.L., Murphy, A.M., 2002. Evaluation of a novel commercial enzyme-linked immunosorbent assay detecting Coxiella burnetiispecific immunoglobulin G for Q fever prevaccination screening and diagnosis. J. Clin. Microbiol. 40, 3526–3529. Henning, K., Sting, R., 2002. Definitive ability of stamp-staining, antigenELISA, PCR and cell culture for the detection of Coxiella burnetii. Berl. Munch. Tierarztl. Wochenschr. 115, 381–384. Khalili, M., Sakhaee, E., Aflatoonian, M.R., Shahabi-Nejad, N., 2011. Herdprevalence of Coxiella burnetii (Q fever) antibodies in dairy cattle farms based on bulk tank milk analysis. Asian Pac. J. Trop. Med. 4, 58–60. Majidzadeh, K., Mohseni, A., Soleimani, M., 2014. Construction and evaluation of a novel internal positive control (IPC) for detection of Coxiella burnetii by PCR. Jundishapur J. Microbiol. 7, e8849. Malou, N., Renvoise, A., Nappez, C., Raoult, D., 2012. Immuno-PCR for the early serological diagnosis of acute infectious diseases: the Q fever paradigm. Eur. J. Clin. Microbiol. Infect. Dis. 31, 1951– 1960.
92
Reply to Letter to the Editor / Preventive Veterinary Medicine 119 (2015) 91–92 ∗ Tel.:
Vongxay, K., Conlan, J.V., Khounsy, S., Dorny, P., Fenwick, S., Thompson, R.C., Blacksell, S.D., 2012. Seroprevalence of major bovine-associated zoonotic infectious diseases in the Lao People’s Democratic Republic. Vector Borne Zoonotic Dis. 12, 861–866.
+34 957 21 87 25; fax: +34 957 21 87 25. E-mail address: [email protected]
Alfonso Carbonero ∗ Department of Animal Health, Veterinary Faculty, University of Cordoba, Córdoba 14006, Spain
6 February 2015