Diagnosis of enteric fever in the emergency department: a retrospective study from Pakistan
© Springer-Verlag London Ltd 2010
Received: 29 May 2009
Accepted: 23 November 2009
Published: 23 March 2010
Enteric fever is one of the top differential diagnoses of fever in many parts of the world. Generally, the diagnosis is suspected and treatment is initiated based on clinical and basic laboratory parameters.
The present study identifies the clinical and laboratory parameters predicting enteric fever in patients visiting the emergency department of a tertiary care hospital in Pakistan.
This is a retrospective chart review of all adult patients with clinically suspected enteric fever admitted to the hospital through the emergency department during a 5-year period (2000–2005).
A total of 421 emergency department patients were admitted to the hospital with suspected enteric fever. There were 53 cases of blood culture-positive enteric fever and 296 disease-negative cases on culture. The mean age in the blood culture-positive group was 27 years (SD: 10) and in the group with negative blood culture for enteric fever, 35 years (SD: 15) with a male to female ratio of 1:0.6 in both groups. Less than half (48%) of all patients admitted with suspected enteric fever had the discharge diagnosis of enteric fever, of which only 13% of the patients had blood culture/serologically confirmed enteric fever. None of the common clinical and laboratory parameters differed between enteric fever-positive patients and those without it.
Commonly cited clinical and laboratory parameters were not able to predict enteric fever.
Enteric fever (EF) encompasses both typhoid and paratyphoid fevers. Typhoid fever is caused by Salmonella typhi, whereas paratyphoid fever is caused by S. paratyphi A, B, and C . Occurring largely in low income countries [2, 3], EF causes 16 million illnesses and 600,000 annual deaths worldwide . It is one of the top differential diagnoses in patients with fever without an obvious source in many parts of the world. In high income countries, EF is suspected in patients with fever and recent history of travel to endemic areas .
The diagnosis of EF in the emergency department (ED) is based on clinical signs and symptoms, with basic or no laboratory testing. Neither the sensitivity of initial diagnosis by the physician is known nor is the diagnostic accuracy of clinical features used for such a diagnosis. This study explores the sensitivity, specificity, positive predictive value, and negative predictive value of common clinical and laboratory parameters used for diagnosing EF in the ED.
A retrospective chart review study was conducted.
Study setting and sample
The hospital’s health information system was used to identify patients admitted to the hospital through the ED with a suspected diagnosis of EF. Medical records were reviewed by trained research assistants. The completed questionnaires were rechecked by the principal investigator for missing information. Information was extracted on: age, gender, presenting signs and symptoms, comorbidities (for example, hypertension and diabetes), and laboratory parameters (for example, hemoglobin, white cell counts, sodium, potassium, and bicarbonate). Diagnosis of typhoid fever was confirmed by blood culture. Blood cultures are the standard diagnostic method. The sensitivity and specificity for identifying blood culture-positive cases of typhoid fever are 89 and 53%, respectively [6, 7].
Measures of diagnostic test accuracy
Comparison of laboratory indices among patients in the different groups (July 2000–June 2005)
Blood culture positive for EF, n = 53
Blood culture negative for EF, n = 296
WBC (× 109/l)
Platelets (× 109/l)
Of all 421 patients suspected of having EF, a little less than half (48%) were discharged with the diagnosis of EF. The diagnoses of the remaining 52% patients were viral fever (21%), malaria (6%), invasive gastroenteritis (5%), urinary tract infection (4%), and upper respiratory tract infection (3%).
Likelihood ratios of clinical and laboratory parameters of blood culture-positive EF (n = 53) versus blood culture negative for EF (n = 296) (July 2000–June 2005)
+ LR (95% CI)
− LR (95% CI)
Past history of EF
Palpable lymph nodes
Our study shows that in an endemic country like Pakistan, about less than half of patients admitted with the diagnosis of suspected EF actually have EF. In non-endemic parts of the world, clinical diagnostic sensitivity is likely to be much lower. In this study, one of the largest ED-based studies, no single clinical or laboratory indicator had a positive LR high enough to help clinical decision-making.
A number of small, non-ED-based studies have looked at the clinical diagnosis of EF. In Indonesia, in a prospective outpatient clinic-based study of 82 pediatric and adult typhoid/paratyphoid patients, Vollaard et al. found a low sensitivity of presenting symptoms. The study failed to find a clinical prediction rule . Similarly, in Nepal, a prospective observational study conducted at a teaching hospital emergency and outpatient department showed that the majority of the symptoms and signs of typhoid in 53 adult cases were without a very high diagnostic accuracy . Many other studies failed to show much difference in the clinical profiles of patients [10–17], though none of these studies evaluated the accuracy of emergency physicians in diagnosing EF.
There were at least two studies where some clinical and laboratory features were found to be highly predictive. In Bangladesh, Haq et al. prospectively studied 106 adult patients with microbiologically confirmed EF comparing them to 170 adult patients with other established febrile illnesses. The study found that history of a stepladder pattern of rise in temperature, loose motions, relative bradycardia, and coated tongue proved to be powerful markers of EF with high specificity (100, 94.7, 94.7, and 94.1%, respectively) . In a study of 130 adult cases, Hosoglu et al. created a prediction rule using seven predictors. These predictors were age <30 years, abdominal distention, confusion, leukopenia, relative bradycardia, positive Widal test, and a typhoid tongue . This prediction rule was validated in the same region where it was developed.
There are several limitations of our study. First, this was a single-center study and may not represent the findings at other centers in Karachi or Pakistan. Second, being an ED-based study, our findings are likely to be applicable to more severe cases as only those who required admission to the hospital were included in this study. Third, due to the retrospective nature of the study, we were limited not only by the completeness of documentation by the treating physician but were also not able to assess all the variables (for example, relative bradycardia). Fourth, there may have been other patients with EF admitted through the ED, but because the clinician did not consider this diagnosis at the time of admission they were not included in this analysis. Fifth, a large number of blood culture negatives could be due to the fact that sensitivity of blood cultures decreases after the first week of illness and also due to prior use of an antibiotic.
In endemic settings, accurate diagnosis of EF via clinical and laboratory findings is difficult in an ED of a tertiary care teaching hospital.
Conflicts of interest
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