A proposed new scoring system for tetanus
INTRODUCTION: Tetanus in adults continues to be a major public health problem in developing countries. Prognosis in tetanus is largely dependent on the various clinical characteristics. This study was carried out to develop a clinical prognostic scoring system according to the natural progression of the disease and to assess its ability to predict the need for specific therapeutic interventions and mortality. MATERIALS AND METHODS: Sixty-five patients were studied, 15 prospectively and 50 retrospectively with an age range between 12 to 70 years. RESULTS: The incubation period was > 7 days in 26 patients (40%), <24 hours in 25 patients (38%), 53 patients (81.5%) had generalized rigidity and 19 (29%) had autonomic dysfunction. Forty-eight (74%) patients needed tracheostomy and 29 (45%) needed mechanical ventilation. The overall mortality was 34%. There was a linear correlation between the grade of tetanus and mortality, (score <2 = 1%, <4 = 3%, >5 = 26%), need for Tracheostomy, (score <4 = 18%, 5 = 26%, >5 = 47%), need for ventilation (scores <4 = 6-8%, 5 = 12%, >5 = 34%), diazepam requirement (scores <4 mean 1500 mg, >5 mean 4000-5000 mg) and duration of ICU stay (score <4 mean of 1 week, > 5 mean 2 to 3 weeks. The overall sensitivity and specificity was 61% and 87% respectively for severe tetanus (score > 6). Multivariate logistic regression analysis showed patients above the age of 50 years (P = 0.003) and need for mechanical ventilation (P = 0.009) were significantly associated with high mortality. DISCUSSION: Prognostication of tetanus with this system was better in comparison with the existing scoring systems in predicting mortality and the need for specific therapeutic interventions. CONCLUSION: The proposed scoring system is a good indicator of the severity of tetanus and use of this system will help in identifying high-risk patients enabling early therapeuticintervention.
Keywords: Tetanus, scoring system, prognosis, grading
Tetanus in adults continues to be a major public health problem in developing countries.,,,, Published data report a mortality around 48 to 50 percent, in young adults, and between 25 to 86% in patients above 30 years of age., Tetanus progresses from mild to a severe phase and then resolves gradually. Since prognosis in tetanus is largely dependent on the various clinical characteristics there have been several attempts to quantify the prognosticating factors by utilizing clinical scoring systems.,,,
A good scoring system should ideally follow the natural progression of the disease and identify high-risk patients so that specific therapeutic interventions can be initiated without delay. In areas where there are limited resources and financial constraints, the role of a prognostic scoring system among patients presenting with tetanus in predicting the need for specific therapeutic interventions (such as mechanical ventilation) and their outcome is helpful in delivering appropriate care.
This study was carried out to develop a clinical prognostic scoring system in adult patients presenting with tetanus according to disease severity. We also made an attempt to validate this prognostic scoring system with the existing ones in predicting the need for specific therapeutic interventions and mortality.
This study was conducted in Christian Medical College and Hospital a tertiary care 1800-bed University Teaching Hospital in South India. Fifteen patients with the clinical diagnosis of tetanus were prospectively recruited into the study. A retrospective chart review of fifty patients over a four-year period was included in the database. The demographic characteristics, onset time (interval between the first symptom and the first spasm) and incubation period (time between injury and first symptom/sign) as well as the need for tracheostomy, the total dose of diazepam, days on mechanical ventilatory support, overall mortality and the duration of ICU stay were ascertained. Autonomic dysfunction was diagnosed if there were two or more of the following. 1. Labile blood pressure, 2. High fever in the absence of infection 3. Tachycardia / dysrhythmia in the absence of fever, 4. Sudden diaphoresis in the absence of fever.,
A score of 1 to 8 was given based on the severity of the disease in [Table - 1].
These 8 scores were compared to the various clinical parameters. Scoring was also done as recommended by Singh et al and by the modified scoring system [Table - 2] derived from Singh and Patel, which is traditionally used for grading tetanus at our institute. This scoring system has been used to assess treatment outcomes in previous trial., Scoring was done at admission and at the end of 24 hours after admission and upgraded if the disease had progressed. All patients received standard treatment for tetanus.,,,
Data from the retrospective and prospective groups of patients were analyzed together. The sensitivity specificity and predictive values for various cut of points in the scores in each scoring system was ascertained. Using these, the various scoring systems were compared with each other to ascertain which one predicts mortality and morbidity best for the scores obtained. This proposed scoring system was compared with two of the three existing scoring systems namely GP Singh et al, and the modified scoring system of Singh and Patel. Joag's scoring system could not be used for comparison due to limited parameters. A risk analysis was done at the end of the study using a multivariate analysis to look at the significance of the variables included in the outcome.
There were a total of 65 patients. Fifteen in the prospective group and fifty in the retrospective group.The age ranged from 12-70 years.Twenty-six (40%) patients had an incubation period of <7 days, 25 (38%) patient had an onset time of <24 hours. Fifty-three (81.5%) patients had generalized rigidity, 19 (29%) had autonomic dysfunction and 39 (60%) had infection during the hospital stay (mostly lower respiratory tract infection). Forty-eight (74%) patients needed tracheostomy, 29 (45%) needed mechanical ventilation and the overall mortality was 22 (34%).
For those patients with a score of < 4 the diazepam requirement was noted to be 1500 mg per 24 hours and for those with a score of 5 and above the diazepam requirement was 4000 to 5000 mg.
Need for Tracheostomy
Among those patients with a score <4 the need for tracheostomy was 18% increasing to 26% among patients with score 5 and 47% in those with a scores of >5. The sensitivity and specificity for predicting the need for tracheostomy was 35% and 76% respectively. Comparison of the present scoring system and the existing system in predicting the need for tracheostomy is given in [Table - 3].
Need for Ventilation
Among patients with a score of < 4 and 5 the need for mechanical ventilatory support was noted in 8% and 12% respectively. Among those with a score of > 5 the need for mechanical ventilatory support increased more than 34%. Comparison of the present scoring system and the existing system in predicting the need for mechanical ventilation is given in [Table - 4].
The mortality in the group of patients with a score of <2 was 1%. The mortality was linearly related to the score, 3% with a score of<4, five percent with a score 5 and 26% with a score of >5. The sensitivity and specificity for predicting outcome were 64% and 85% respectively.Comparison of the effect of each scoring system on mortality is given in [Table - 5].
Duration of ICU stay
The mean duration of ICU stay was one week for those patients with a score <4 and for those with a score >5 the mean duration of stay was two to three weeks. Comparison of the scoring systems in predicting duration of ICU stay are given in [Table - 6].
Risk factor analysis
Multivariate logistics regression analysis showed that patients above the age of 50 years (P = 0.003) and the need for mechanical ventilation (P = 0.009) were independently associated with high mortality. There was no significant statistical association noted with mortality in those presenting with rigidity (P = 0.370), spasms (P = 0.289), autonomic dysfunction (P = 0.790) and in those who required tracheostomy (P = 0.282). The overall sensitivity was 61% and specificity of 87% for patients with severe tetanus (score > 6). The sensitivity and specificity values for different scoring systems are given in respective tables.
Several 'scoring systems' have been designed in the past to assess the severity of tetanus by using certain clinical parameters.,,, A numerical score is given according to the clinical symptom and signs and the patient classified to have mild, moderate or severe disease. Tetanus follows a natural progression, which is well identifiable by clinical manifestations. Spasms occurs as a neuromuscular manifestation in tetanus, and indicate a severe form of disease in the absence of other parameters. Therefore a good scoring system should center on this dangerous manifestation of the disease.
Though the existing scoring systems are excellent in assessing the severity of tetanus, there are a few practical problems such as inclusion of the incubation period and onset time in grading tetanus.,, Many patients may not recall an injury, and the assessment of the 'incubation period' becomes difficult .In some cases spores may lie dormant for a long period before the disease manifests. Patients who present with severe spasms and advanced disease are unable to give an accurate history and paradoxically high or low scores may be obtained because of cofounding factors in the history.
The scoring system adopted in this present study however is based on the natural progression of the disease and the clinical presentation and any patient can be assigned a grade of severity with a simple clinical assessment without other confusing parameters.
In the present study the scoring system showed a sharp increase in the mortality and morbidity once the spasms had become significant (score >5). We could infer that any patient with a score >5 has a high likelihood of needing tracheostomy and requires close follow up during the initial period, and may need ventilatory support. It is important to assess the need for ventilation because it is shown that the utilization of early ICU services and mechanical ventilatory support along with other supportive measures reduces the mortality in tetanus.,
In this present study mortality among patients who required mechanical ventilation was high indicating that these patients have a far advanced and serious disease. Giving a score for mechanical ventilation as done in the present study is useful in predicting the outcome. Earlier studies have shown that significant autonomic dysfunction occur among patients with tetanus.,, In this present study 29% of the patients were noted to have autonomic dysfunction.
The proposed new scoring system had a prognostic value in tetanus and predicted the need for specific therapeutic interventions (mechanical ventilation). There was a linear correlation between the increasing grade and increasing mortality and morbidity. The linear correlation was also consistent in the other outcome parameters like need for tracheostomy and ventilation. Among patients presenting with severe tetanus the overall sensitivity was 61% and specificity was 87% in the new scoring system.
There were some limitations in this study. The prospective study group had a relatively small number of patients. Though this was balanced by the combination of the prospective and retrospective study, it would be ideal to study a larger group prospectively. Further prospective studies are needed to validate this proposed scoring system.
The proposed scoring system is a useful in grading the severity of tetanus and in predicting mortality.The use of this system will be helpful in identifying high risk patients enabling one to intervene early with therapeutic measures such as tracheostomy and mechanical ventilation.
We thank Mr. Jamal from the clinical Epidemology unit and all the staff members from the Intensive care unit, Christian Medical College and Hospital, Vellore, India for his valuable support during this study.
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5], [Table - 6]