Scandinavian Journal of Infectious Diseases
ISSN: 0036-5548 (Print) 1651-1980 (Online) Journal homepage: http://www.tandfonline.com/loi/infd19
The Nitroblue Tetrazolium (NBT) Test and White Blood Cell Count in Acute Throat Infections Bengt Björkstén, Tom Ekstrand, Leif Gothefors & Yngve Östberg To cite this article: Bengt Björkstén, Tom Ekstrand, Leif Gothefors & Yngve Östberg (1975) The Nitroblue Tetrazolium (NBT) Test and White Blood Cell Count in Acute Throat Infections, Scandinavian Journal of Infectious Diseases, 7:1, 45-49, DOI: 10.3109/inf.1975.7.issue-1.08 To link to this article: http://dx.doi.org/10.3109/inf.1975.7.issue-1.08
Published online: 02 Jan 2015.
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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=infd19 Download by: [RMIT University Library]
Date: 17 April 2016, At: 07:53
Scand J Infect Dis 7: 45-49, 1975
The Nitroblue Tetrazolium (NBT) Test and White Blood Cell Count in Acute Throat Infections BENGT BJORKSTEN, TOM EKSTRAND, LEIF GOTHEFORS and YNGVE OSTBERG
Downloaded by [RMIT University Library] at 07:53 17 April 2016
From the Departments of Virology, Otorhinolaryngology and Infectious Diseases, University Hospital, Umeii, Sweden
ABSTRACT. The clinical value of the NBT test and of leucocyte counts in the aetiological differentiation of acute throat infections was investigated. In our hands a frequency ofless than 13 % NBT positive neutrophils is considered as normal and a test value above 19% as "positive", i.e, indicating a bacterial infection. More than 19 % or more than 1800 NBT positive neutrophils per mm" blood were found in 10 of 18 patients with an infection caused by beta-haemolytic streptococci, in 1of2 patients with a Mycoplasma pneumoniae infection and in 1 patient with both a streptococcal and mycoplasmal infection, but in none of 19 patients with a viral infection. Since 8 of 18 patients with streptococcal throat infection had normal NBT test results, the NBT test apparently is of limited value in the early recognition of these infections. A high NBT test value would however support the diagnosis. The white blood cell and neutrophil counts were of little value in the differentiation between streptococcal and viral throat infection.
INTRODUCTION Not even the experienced otorhinolaryngologist can differentiate between streptococcal, mycoplasmal and viral throat infections solely by clinical inspection (6). Since cultivation of microorganisms is time-consuming and measurable immune response has a certain delay, there is an obvious need for a method that would allow a rapid distinction between streptococcal and non-streptococcal throat infections, i.e, between infections where on one hand penicillin treatment is valuable and on the other hand where such a treatment is useless or might even be harmful. The NBT test introduced by Parketal. in 1968(14) has been suggested as an aid in the differential diagnosis between bacterial and non-bacterial infections (5, 9, 12, 13). However, later reports have yielded controversial results and the clinical value of the NBT tests has been questioned (16). In two recent studies (1,2) it was shown that minor changes in the performance of the test could cause marked changes in the test results. Thus a strictly standardized technique is necessary in order to correctly evaluate the use of the NBT test in different infections. In this paper we report on the NBT test results in healthy adults and healthy full-term newborn in-
fants. The NBT test was also evaluated in patients with acute throat infection. MATERIAL AND METHODS Study groups To evaluate the NBT test results in healthy persons, NBT tests were performed on blood samples from 95 healthy adults (age 17-55 years, mean 28 years). Since newborn infants are reported to have elevated NBTtest values (3, 8), 23 blood samples from the umbilical veins of healthy fullterm newborn babies were used as "positive controls" on the NBT test method used. To evaluate the NBT test results in patients with acute throat infections we studied 40 patients (age 8-65 years, mean 19 years), attending the departments of otorhinolaryngology and infectious diseases for sore throat. Only patients with a sore throat for less than 4 days and with no other signs of respiratory tract infection were included. All patients treated with antibiotics during the last 3 weeks prior to the investigation were excluded, as well as patients with other diseases. Fever of more than 38°C was found in 35 of the patients. An evaluation of clinical signs of sore throat was done by the physician. The size of the tonsils, the redness of the tonsils and the pharyngeal wall, the presence of visible detritus plugs in the tonsils and the size and tenderness of the cervical lymph nodes were evaluated according to a 3-grade scale of each item. The physician also recorded his impression of whether the infection was caused by betahaemolytic streptococci or not. Patients with symptoms and signs indicating a bacterial infection were treated with penicillin. All patients were called for a second visit 2-3 Scand J Infect Dis 7
46
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count (WBC) (thousands per mm") and differential count ofWBC (100 leucocytes counted).
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Number of patients Mean SE
95
23
4.6
29.5
0.4
3.1
SD
3.8
14.7
Fig. I. NET test results in 95 healthy adults (A) and 23 healthy full-term newborn babies (B).
weeks after their first visit. The clinical signs were then re-evaluated and the laboratory investigations repeated. NBT test and haematological investigations The NBT test was performed on venous blood according to the method described by Park et al. (14) but slightly modified in our laboratory (2). The total number of NBT positive neutrophils was determined by multiplying the number of neutrophils per mrn" blood by the proportion of NBT positive neutrophils. Proportions of 20 % or higher and a total number of at least 1800 NBT positive neutrophils per rnm" blood were considered as significantly elevated test values. The following haematological investigations were performed: ESR (mm per hour), total white blood cell
Isolation attempts Throat swab specimens were used for isolation of streptococci, mycoplasmas and viruses and were transported without delay to the laboratory. Specimens intended for isolation of streptococci were transported on Chocolate Agar Slants (BBL lab., Baltimore, Maryland, USA) and specimens intended for isolation of mycoplasmas and viruses were kept in a transport medium composed of 0.2 g egg albumin in 100 ml saline buffered with 1.5 ml of a 2 M solution of HEPES (pH 7.4). In tubes intended for virus isolation 10 mg gentamicin per 100 ml medium was added. Streptococci were cultivated on blood agar plates and haemolytic colonies were checked for production of soluble haemolysin and for bacitracin and penicillin sensitivity. If the streptococci produced soluble haemolysin and were sensitive for bacitracin and penicillin they were referred to as "probably group A streptococci". No serological grouping was performed. Swabs for isolation of viruses were inoculated into diploid human embryonic lung cells and Vero-cells. Positive specimens were subcultivated using the same sort of cells and the type of virus was identified by serological methods (neutralisation or complement fixation tests). For isolation of mycoplasmas, swabs were inoculated into Mycoplasma Broth or on Mycoplasma Agar (Difco laboratories, Detroit, Michigan, USA) containing 20% horse serum and 10% yeast extract. Duplicate plates and broths were incubated at 37°C in air with 10% CO2 and anaerobically in jars with 95% N 2 and 5 % CO2 • The mycoplasmas were identified by the development of typical colonies and further by colony growth inhibition around discs impregnated with specific antisera. The specific mycoplasma antisera were obtained from BBL lab., Baltimore, Maryland, USA. Serological tests The following serological tests were done according to methods in general use: titration of complement-fixing (CF) antibodies against Mycoplasma pneumoniae, influenza A
Table I. Results of NBT tests, WBe counts and ESR in 40 patients with acute throat infections % NBT positive neutrophils
ISSN: 0036-5548 (Print) 1651-1980 (Online) Journal homepage: http://www.tandfonline.com/loi/infd19
The Nitroblue Tetrazolium (NBT) Test and White Blood Cell Count in Acute Throat Infections Bengt Björkstén, Tom Ekstrand, Leif Gothefors & Yngve Östberg To cite this article: Bengt Björkstén, Tom Ekstrand, Leif Gothefors & Yngve Östberg (1975) The Nitroblue Tetrazolium (NBT) Test and White Blood Cell Count in Acute Throat Infections, Scandinavian Journal of Infectious Diseases, 7:1, 45-49, DOI: 10.3109/inf.1975.7.issue-1.08 To link to this article: http://dx.doi.org/10.3109/inf.1975.7.issue-1.08
Published online: 02 Jan 2015.
Submit your article to this journal
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=infd19 Download by: [RMIT University Library]
Date: 17 April 2016, At: 07:53
Scand J Infect Dis 7: 45-49, 1975
The Nitroblue Tetrazolium (NBT) Test and White Blood Cell Count in Acute Throat Infections BENGT BJORKSTEN, TOM EKSTRAND, LEIF GOTHEFORS and YNGVE OSTBERG
Downloaded by [RMIT University Library] at 07:53 17 April 2016
From the Departments of Virology, Otorhinolaryngology and Infectious Diseases, University Hospital, Umeii, Sweden
ABSTRACT. The clinical value of the NBT test and of leucocyte counts in the aetiological differentiation of acute throat infections was investigated. In our hands a frequency ofless than 13 % NBT positive neutrophils is considered as normal and a test value above 19% as "positive", i.e, indicating a bacterial infection. More than 19 % or more than 1800 NBT positive neutrophils per mm" blood were found in 10 of 18 patients with an infection caused by beta-haemolytic streptococci, in 1of2 patients with a Mycoplasma pneumoniae infection and in 1 patient with both a streptococcal and mycoplasmal infection, but in none of 19 patients with a viral infection. Since 8 of 18 patients with streptococcal throat infection had normal NBT test results, the NBT test apparently is of limited value in the early recognition of these infections. A high NBT test value would however support the diagnosis. The white blood cell and neutrophil counts were of little value in the differentiation between streptococcal and viral throat infection.
INTRODUCTION Not even the experienced otorhinolaryngologist can differentiate between streptococcal, mycoplasmal and viral throat infections solely by clinical inspection (6). Since cultivation of microorganisms is time-consuming and measurable immune response has a certain delay, there is an obvious need for a method that would allow a rapid distinction between streptococcal and non-streptococcal throat infections, i.e, between infections where on one hand penicillin treatment is valuable and on the other hand where such a treatment is useless or might even be harmful. The NBT test introduced by Parketal. in 1968(14) has been suggested as an aid in the differential diagnosis between bacterial and non-bacterial infections (5, 9, 12, 13). However, later reports have yielded controversial results and the clinical value of the NBT tests has been questioned (16). In two recent studies (1,2) it was shown that minor changes in the performance of the test could cause marked changes in the test results. Thus a strictly standardized technique is necessary in order to correctly evaluate the use of the NBT test in different infections. In this paper we report on the NBT test results in healthy adults and healthy full-term newborn in-
fants. The NBT test was also evaluated in patients with acute throat infection. MATERIAL AND METHODS Study groups To evaluate the NBT test results in healthy persons, NBT tests were performed on blood samples from 95 healthy adults (age 17-55 years, mean 28 years). Since newborn infants are reported to have elevated NBTtest values (3, 8), 23 blood samples from the umbilical veins of healthy fullterm newborn babies were used as "positive controls" on the NBT test method used. To evaluate the NBT test results in patients with acute throat infections we studied 40 patients (age 8-65 years, mean 19 years), attending the departments of otorhinolaryngology and infectious diseases for sore throat. Only patients with a sore throat for less than 4 days and with no other signs of respiratory tract infection were included. All patients treated with antibiotics during the last 3 weeks prior to the investigation were excluded, as well as patients with other diseases. Fever of more than 38°C was found in 35 of the patients. An evaluation of clinical signs of sore throat was done by the physician. The size of the tonsils, the redness of the tonsils and the pharyngeal wall, the presence of visible detritus plugs in the tonsils and the size and tenderness of the cervical lymph nodes were evaluated according to a 3-grade scale of each item. The physician also recorded his impression of whether the infection was caused by betahaemolytic streptococci or not. Patients with symptoms and signs indicating a bacterial infection were treated with penicillin. All patients were called for a second visit 2-3 Scand J Infect Dis 7
46
B. Bjorksten et al. A .!!!. J:: a.
e
-
count (WBC) (thousands per mm") and differential count ofWBC (100 leucocytes counted).
B
55 50
:::J
Q)
c:
40
Q)
...
>
'iii 0 a.
30
I-
al
Z
20
'0
c: Q)
.
I····
10 .:
o
Downloaded by [RMIT University Library] at 07:53 17 April 2016
&
·fi:::~....
::!::::::::::..... 0········
Number of patients Mean SE
95
23
4.6
29.5
0.4
3.1
SD
3.8
14.7
Fig. I. NET test results in 95 healthy adults (A) and 23 healthy full-term newborn babies (B).
weeks after their first visit. The clinical signs were then re-evaluated and the laboratory investigations repeated. NBT test and haematological investigations The NBT test was performed on venous blood according to the method described by Park et al. (14) but slightly modified in our laboratory (2). The total number of NBT positive neutrophils was determined by multiplying the number of neutrophils per mrn" blood by the proportion of NBT positive neutrophils. Proportions of 20 % or higher and a total number of at least 1800 NBT positive neutrophils per rnm" blood were considered as significantly elevated test values. The following haematological investigations were performed: ESR (mm per hour), total white blood cell
Isolation attempts Throat swab specimens were used for isolation of streptococci, mycoplasmas and viruses and were transported without delay to the laboratory. Specimens intended for isolation of streptococci were transported on Chocolate Agar Slants (BBL lab., Baltimore, Maryland, USA) and specimens intended for isolation of mycoplasmas and viruses were kept in a transport medium composed of 0.2 g egg albumin in 100 ml saline buffered with 1.5 ml of a 2 M solution of HEPES (pH 7.4). In tubes intended for virus isolation 10 mg gentamicin per 100 ml medium was added. Streptococci were cultivated on blood agar plates and haemolytic colonies were checked for production of soluble haemolysin and for bacitracin and penicillin sensitivity. If the streptococci produced soluble haemolysin and were sensitive for bacitracin and penicillin they were referred to as "probably group A streptococci". No serological grouping was performed. Swabs for isolation of viruses were inoculated into diploid human embryonic lung cells and Vero-cells. Positive specimens were subcultivated using the same sort of cells and the type of virus was identified by serological methods (neutralisation or complement fixation tests). For isolation of mycoplasmas, swabs were inoculated into Mycoplasma Broth or on Mycoplasma Agar (Difco laboratories, Detroit, Michigan, USA) containing 20% horse serum and 10% yeast extract. Duplicate plates and broths were incubated at 37°C in air with 10% CO2 and anaerobically in jars with 95% N 2 and 5 % CO2 • The mycoplasmas were identified by the development of typical colonies and further by colony growth inhibition around discs impregnated with specific antisera. The specific mycoplasma antisera were obtained from BBL lab., Baltimore, Maryland, USA. Serological tests The following serological tests were done according to methods in general use: titration of complement-fixing (CF) antibodies against Mycoplasma pneumoniae, influenza A
Table I. Results of NBT tests, WBe counts and ESR in 40 patients with acute throat infections % NBT positive neutrophils
