© Borgis - New Medicine 3/1999, s. 24-25
Michał Grzegorowski, Jarosław Antyborzec, Jarosław Szydłowski
NBT test in children with subglottic laryngitis
Department of Pediatric Otolaryngology, Institute of Pediatrics, Medical Academy, Poznań
Head: Prof. Michał Grzegorowski, M.D.
Summary
In 1968 Park and co-workers introduced the NBT test which was used in recognition of bacterial infection. Subglottic laryngitis (SL) is caused by viruses, but in the second stage of this disease bacterial infection may occur.
The aim of this study is assesment of the value of the NBT test in children with SL before and after treatment.
Examination of the values given by the NBT test were performed twice in 60 children with SL and once in 26 children as the control group. We observed a statistical difference between the results of the test in children with SL by admission and after 57 days of treatment.
According to the results of the test in children under 3 years of age, especially in a severe case of SL, antibiotic treatment is recommended.
In 1968 Park and co-workers introduced a spontaneous test for reducing nitroblue tetrazolium, which was used for recognition of bacterial infections (7). The NBT test concept is based on the hypothesis that a metabolic change and an increased reduction of nitroblue tetrazolium dye would take place when leukocytes are involved in phagocytosis in vivo during a natural infection. A significant increase in test values was observed not only in bacterial diseases such as bacterial meningitis, bacterial endocarditis, osteomyelitis, peritonitis, pneumonia etc., but also in malaria, miliar tuberculosis, chronic granulomatous disease, and in the newborn (3, 8). Some authors reported that the level of this test is higher in neoplasms (6, 9).
The etiology of subglottic laryngitis (SL) is not homogenous (1, 2). It is thought that viruses are the direct cause. In the second stage of the illness bacterial infection may be found (4).
The aim of this work is the estimation of the values of the NBT test in children with subglottic laryngitis, before and after treatment, and comparison with the results obtained from children in a control group.
Material and method
In 60 children with SL aged 18 months to 10 years double examinations of the values of the NBT test were performed.
The first examination was performed at 8.00 a.m., on the day of admission to the clinic. The second was performed on the 5-7th day of treatment at the same time. Children with SL were divided into 2 groups. In the younger group there were 31 children up to 3 years of age, and in the older group 29 children. Twenty-six children of the control group never had SL and were healthy during the examination.
The NBT test was performed according to the Park and co-workers method. Blood for examination was placed in plastic test tubes. After staining the smears were examined under a light microscope and 100 neutrophiles were counted. Only those with a large black deposit were considered to be NBT positive. Statistical analysis was performed by the Willcoxon and Mann Whitney test.
Results
The results of the NBT testing after admission, in examinations performed on children with SL in both older and younger groups did not differ from the value from the test in children from the control group (Table 1).
Table 1. Results of nbt-test depending on age (%).
| Group | Before treatment (A) | 5-7 days after treatment (B) | Statistical difference (A/B) |
| Younger (n = 31) | 12.9 ± 7.4 | 23.2 ± 13.2 | p <0.05 |
| Older (n = 29) | 13.1 ± 5.6 | 20.7 ± 9.3 | p <0.05 |
| Control (n = 26) | 12.5 ± 3.0 | - | - |
Comparing the results of the test after admission and after 5-7 days of treatment in younger and older children, we observed a statistical difference.
Also, in considering the results of the test after admission and 5-7 days of treatment, depending on the degree of disease, we noticed a statistical difference between the 1st and 2nd stages of the disease.
In the 3rd degree the difference was not reconted but at this degree of SL the arithmetical average after admission was the highest (Table 2).
Table 2. Results of NBT-test depending on degree of disease (%) (average ± SD).
| Degree of disease | Before treatment (A) | 5-7 days after treatment (B) | Statistical difference (A/B) |
| I (n = 28) | 11.6 ± 5.9 | 18.5 ± 8.7 | p <0.01 |
| II (n = 27) | 14.0 ± 7.4 | 25.2 ± 13.8 | p <0.01 |
| III (n = 5) | 15.6 ± 2.6 | 24.6 ± 5.7 | - |
Discussion
Park and co-workers reported that the nitroblue tetrazolium dye test might be useful in differentiating patients with bacterial infection from individuals with non-bacterial disease.
The results of the NBT test after admission in children with SL prove, in the 1st stage of the disease, the appearance of virus infection. There was no statistical difference between the results of the NBT test in younger and older groups. It is well known that higher results from the NBT test may appear in newborns (5).
The NBT test is not related to bacterial infection, but can be used for monitoring its course. The results of NBT show that viruses play the most important role in SL, in the first days of infection. Examinations performed after 5-7 days of treatment revealed a considerable growth in the results of the NBT test and indicate bacterial infection in the next part of disease. The results of the test were higher in spite of treatment. We used simple glycocorticosteroids and antibiotics as such synthetic penicillin.
These are medicines which do not significantly influence the phagocytosis - they should not affect the results of the NBT test. The mechanism for reduction of NBT dye to produce formazan in the cytoplasm of phagocytes is not entirely clear (3).
Thanks to the results of the NBT test, we can recommend antibiotic treatment in children under 3 years of age especially with a severe course of disease. Inflammation from SL in older children does not spread so quickly into the lower respiratory tract, so antibiotic treatment is not necessary.
Conclusions
1. The NBT test may be clinically useful as a diagnostic aid differentiating certain non-bacterial illnesses from others.
2. The low percentage of NBT at admission shows that viruses play a major role in the etiology of SL.
3. According to the results of the test after 5-7 days in children under 3 years of age, especially in severe course of SL, antibiotic treatment is recommended.
Piśmiennictwo
1. Biesalski P.: Die stenosierende Laryngo-Tracheitis im Kindesalter. Z. Laryng. Rhinol. 1956, 35:226- 236. 2. Denny F.W. et al.: Croup: An 11 year study in a pediatric practice. Pediatrics 1983, 71:871-876. 3. Feigin R.D. et al.: Nitroblue tetrazolium dye test as an aid in the differential diagnosis of febrile disorders. J. of Pediatrics 1971, 78:230-237. 5. Fried M.P.: Controversies in the management of supraglottitis and croup. Pediatr. Clin. North. Am. 1979, 26:931-942. 6. Humbert J.R. et al.: Increased reduction of nitroblue tetrazolium by neutrophils of newborn infants. Pediatrics 1970, 45:125-128. 7. Kuniar J.B., Kopeć W.: Nitroblue - tetrazolium reductions test (NBT) in patients with laryngeal carcinoma. Otolaryng. Pol. 1980, 34:207-210. 8. Park B.H. et al.: Infection and nitroblue tetrazolium reduction by neutrophils. Lancet 1968, 2:532-533. 9. Park B.H.: The use and limitations of the nitroblue tetrazolium test as a diagnostic aid. J. of Pediatrics 1971, 78:376-378. 10. Sułowicz W. et al.: Spontaneous and latex stimulated NBT Reduction by neutrophil granulocytes in peripheral blood of patients with neoplasms. PTL 1982, 37:1201-1203.
