Year : 2016 | Volume
: 19 | Issue : 3 | Page : 414--416
Anti-cysticercus antibody detection in saliva as a potential diagnostic tool for neurocysticercosis
Rumpa Saha1, Priyamvada Roy1, Shukla Das1, Dheeraj Shah2, Sunil Agarwal3, Iqbal Rajinder Kaur1,
1 Department of Microbiology, University College of Medical Sciences and Guru Teg Bahadur Hospital, New Delhi, India
2 Department of Pediatrics, University College of Medical Sciences and Guru Teg Bahadur Hospital, New Delhi, India
3 Department of Medicine, University College of Medical Sciences and Guru Teg Bahadur Hospital, New Delhi, India
Department of Microbiology, University College of Medical Sciences and Guru Teg Bahadur Hospital, New Delhi - 110 095
Objectives: This study was planned to determine the usefulness of anti-cysticercus IgG antibody detection in saliva for neurocysticercosis (NCC) diagnosis, along with serum C-reactive protein (CRP) level to serve as a surrogate marker. Materials and Methods: In this prospective study of 14 months duration, blood and saliva samples were collected from 40 patients suspected to be suffering from NCC and were subjected to anti-cysticercus IgG antibody detection by ELISA. Serum CRP levels were estimated as acute-phase reactant by high sensitivity CRP ELISA. Results: Anti-cysticercus IgG was detected in serum and saliva of 34 and 30 patients, respectively. Cases positive for salivary antibody were positive for serum antibody and their serum CRP level was higher than normal. Cases negative for salivary antibody had low serum CRP levels. Anti-cysticercus IgG detection in saliva was 88.24% sensitive, 100% specific, and had a positive predictive value of 100% and negative predictive value of 60%. Positive salivary anti-cysticercus IgG and high serum CRP level showed a significant association. Difference between CRP levels of patients positive for anti-cysticercus antibody in both serum and saliva, and patients positive for antibody in serum but not saliva was highly significant. Conclusions: Saliva, being painless and noninvasive, can be used as alternative to serum for NCC diagnosis.
|How to cite this article:|
Saha R, Roy P, Das S, Shah D, Agarwal S, Kaur IR. Anti-cysticercus antibody detection in saliva as a potential diagnostic tool for neurocysticercosis.Ann Indian Acad Neurol 2016;19:414-416
|How to cite this URL:|
Saha R, Roy P, Das S, Shah D, Agarwal S, Kaur IR. Anti-cysticercus antibody detection in saliva as a potential diagnostic tool for neurocysticercosis. Ann Indian Acad Neurol [serial online] 2016 [cited 2021 Sep 21 ];19:414-416
Available from: https://www.annalsofian.org/text.asp?2016/19/3/414/179972
Neurocysticercosis (NCC) is considered to be the most common helminthic infestation of the central nervous system.  NCC occurs worldwide. However, it has a highly variable prevalence, depending mainly on sociocultural and economic factors.  NCC has become an important emerging infection in the industrialized regions because of increased travel and influx of immigrants from endemic areas.  Cysticercosis is a major public health problem in the developing countries, particularly India and Southeast Asian countries. ,, In most developing areas of the world, 10% of acute neurological cases are patients with NCC. 
NCC is caused by infection of the brain with encysted larvae of the tapeworm Taenia solium.  It may be asymptomatic or may cause a variety of clinical manifestations depending on the number, location, and stage of the development of the cysticercus-associated lesions. Epileptic seizures, hydrocephaly, and intracranial hypertension, in this order, are the most frequent clinical features.  The clinical diagnosis of NCC usually requires magnetic resonance imaging or computed tomography brain scans, but they may not be able to completely differentiate it from tuberculoma.  Neurohydatidosis, which is an important cause of intracranial space occupying lesion and may have clinical features similar to NCC, is relatively rare in India.  Detection of specific anti-cysticercus antibodies by Enzyme-linked Immunoelectrotransfer Blot and Western Blot is also supportive of NCC diagnosis. However, detection of IgG antibodies for T. solium may occur for cysticerci located anywhere in the body and not necessarily in the brain.  Saliva may provide a painless, noninvasive, and simple sampling method for diagnostic assay. , C-reactive protein (CRP) level in the serum is also a useful acute-phase reactant which may serve as a marker of NCC.  This study was thus planned to compare the diagnostic utility of serum and saliva samples for the diagnosis of NCC and to evaluate the role of CRP as a surrogate marker for the same.
Materials and Methods
This 14 months prospective study (September 1, 2014-October 31, 2015) was carried at our 1500 bedded tertiary care Government Hospital in Delhi, after clearance from the Institutional Ethical Committee. Forty patients clinically and radiologically suspected to be suffering from NCC and presenting to the hospital (Department of Medicine and Pediatrics) during the study period were included in the study.
Sampling and analysis
The subjects were sampled for 5 ml of blood and saliva samples. Serum was separated and stored at −20°C until tested.
For saliva collection, the subjects were asked to refrain from eating, drinking, or oral hygiene procedures for at least 1 h, after which they were given distilled drinking water and asked to rinse their mouth out well for 1 min. The subjects could then expectorate or swallow the water. The participants waited 10 min before commencing with the collection. Resting drooling method was used to collect saliva. Subjects were asked to sit in an upright position and tilt their heads down slightly to pool saliva in the mouth. The first expectoration was discarded. Subsequently, 5 ml saliva was then expectorated into a prelabeled sterile container. The samples were then immediately placed on ice to minimize degradation of salivary proteins until further processing.  They were immediately transported to the laboratory. Within 1 h, the samples were subjected to a single freeze-thaw cycle to break down mucopolysaccharides that can interfere with pipetting. Then, the samples were frozen (−20°C) until assayed.
The samples were subjected to anti-cysticercus IgG antibody detection by DRG T. solium IgG (cysticercosis) EIA kit (DRG International Inc., Springfield New Jersey, USA). Quantitative determination of CRP as acute-phase reactant was done in the serum samples by DRG CRP, high sensitivity (HS)-CRP EIA kit (DRG International Inc., Springfield New Jersey, USA). Frequency distributions were obtained, and percentages were calculated using SPSS version 16.0 (Chicago, SPSS Inc). P value was calculated using Fisher's exact test and Mann-Whitney test as appropriate.
Anti-cysticercus IgG was detected in serum and saliva of 34 (85%) and 30 (75%) subjects, respectively. Subjects positive for salivary antibody were positive for serum antibody as well as but not vice-versa.
The 30 study subjects positive for anti-cysticercus IgG antibody in saliva had high serum CRP levels, i.e., more than 8.2 mg/L. Rest of the study subjects who tested negative for salivary anti-cysticercus IgG antibody had low serum CRP levels. The 6 study subjects negative for anti-cysticercus IgG antibody in either sample also had low serum CRP levels. Positive salivary anti-cysticercus IgG antibody and high serum CRP levels showed a strong association (P < 0.001, confidence interval [CI] = 95%). Among the patients positive for anti-cysticercus antibody in both serum and saliva, the median CRP level and interquartile range were 10.0430 mg/L and 2.8316 mg/L, respectively, whereas among the patients positive for anti-cysticercus antibody in serum but not in saliva, the median CRP level and interquartile range were 1.9986 mg/L and 3.7112 mg/L, respectively. This difference was also highly significant (P < 0.001, CI = 95%).
A total of 24 (60%) samples were received from males, whereas 16 (40%) were from females. Among the males, the antibodies were detected in both serum and saliva samples in 14 (58.33%), whereas 4 (16.67%) were positive only in serum. Six (25%) tested negative for the antibodies in either sample. However, all 16 (100%) females enrolled in this study were positive for the antibodies in serum as well as saliva. The difference in positivity for salivary antibodies in the 2 sexes was also significant (P = 0.0026, CI = 95%).
The range, mean, and median age in the study were 1-55, 23, and 20.5 years, respectively. A maximum number of positive serum samples (18, 52.94%) belonged to patients aged between 1 and 15 years. These patients tested positive for the antibodies in saliva as well. Sixteen (47.06%) positive serum samples were from patients of higher ages, and among them, 12 (75%) were saliva positive and 4 (25%) were saliva negative.
Majority of the study subject's positive for serum anti-cysticercus IgG antibody demonstrated the antibodies in saliva as well. Anti-cysticercus IgG antibody detection in saliva was found to be 88.24% sensitive, 100% specific, and had a positive predictive value of 100% and a negative predictive value of 60%. In a study done previously on utility of antibody detection in saliva for diagnosis of NCC in Mexico by Feldman et al., saliva was found to be more sensitive in EIA than serum.  E Acosta also carried out a study in Mexico in which he found that detection of anti-cysticercus IgG antibodies in saliva by ELISA may be used in the diagnosis of NCC.  Nevertheless, currently, the standard protocol for diagnosis of NCC involves antibody detection in serum and not saliva. However, since we found antibody detection in saliva to have 100% specificity and positive predictive value, we recommend using saliva for initial screening for NCC as it is a noninvasive sample, and in case of a negative outcome, antibody detection can be done in serum.
Positive salivary anti-cysticercus IgG antibody displayed a strong association with high serum CRP level (P < 0.001, CI = 95%). It was found that CRP was significantly raised in patients positive for salivary antibodies and was within the normal range in the rest even if antibodies were found in their serum. CRP, being an acute-phase reactant, serves as a useful indicator of inflammatory processes.  Hence, it may be inferred from the above results that during acute inflammation (as demonstrated by significantly raised CRP) anti-cysticercus IgG antibody reaches saliva in addition to blood. Furthermore, the presence of salivary antibody may prove to be valuable in predicting the disease prognosis as it is associated with high CRP level, which in turn is suggestive of intense inflammatory reaction.
Although most of the study samples were received from males (male:female = 3:2), serum positivity was more in females compared to males (75% vs. 100%). It was found that antibody positivity in saliva and high serum CRP levels were seen among only 14 (77.78%) of the 18 serum antibody positive males, whereas it was present in all (100%) females. The findings are similar to those reported from previous studies. ,, Fleury et al. found higher cerebrospinal fluid leukocyte counts in females compared to males and suggested that immune-endocrinological factors play a role in pathogenesis of NCC and are responsible for more inflammation during NCC in women. 
Most of positive serum samples belonged to patients between 1 and 15 years of age, and these patients tested positive for the antibodies in saliva also. This is in agreement with findings reported by Kumar et al. and they have stated that commonly young people below 20 years of age are affected as this generation generally observes minimal precautions. 
Saliva provides a useful painless, noninvasive, and simple sampling method for the diagnosis of NCC. Since it has 100% specificity and 100% positive predictive value, it can be used initially to detect cysticercosis and provide supportive evidence of NCC diagnosis. If NCC is strongly suspected in spite of negative salivary antibodies, serum may be tested for anti-cysticercus antibody. Saliva is useful particularly in the pediatric age-group in which blood sample collection often may be difficult. Moreover, in already collected blood sample, HS-CRP level may serve as a valuable surrogate marker for the diagnosis of NCC.
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