Modification of the Conventional Influenza Epidemic Models Using Environmental Parameters in Iran / 대한의료정보학회지

OBJECTIVES: The association between the spread of infectious diseases and climate parameters has been widely studied in recent decades. In this paper, we formulate, exploit, and compare three variations of the susceptible-infected-recovered (SIR) model incorporating climate data. The SIR model is a well-studied model to investigate the dynamics of influenza viruses; however, the improved versions of the classic model have been developed by introducing external factors into the model. METHODS: The modification models are derived by multiplying a linear combination of three complementary factors, namely, temperature (T), precipitation (P), and humidity (H) by the transmission rate. The performance of these proposed models is evaluated against the standard model for two outbreak seasons. RESULTS: The values of the root-mean-square error (RMSE) and the Akaike information criterion (AIC) improved as they declined from 8.76 to 7.05 and from 98.12 to 93.01 for season 2013/14, respectively. Similarly, for season 2014/15, the RMSE and AIC decreased from 8.10 to 6.45 and from 117.73 to 107.91, respectively. The estimated values of R(t) in the framework of the standard and modified SIR models are also compared. CONCLUSIONS: Through simulations, we determined that among the studied environmental factors, precipitation showed the strongest correlation with the transmission dynamics of influenza. Moreover, the SIR+P+T model is the most efficient for simulating the behavioral dynamics of influenza in the area of interest.

Anal sphincter injuries during hemorrhoidectomy: a multi center study

Hemorrhoidectomy is the treatment of choice for patients with third or fourth-degree hemorrhoids. Although the majority of surgeons believe that surgical hemorrhoidectomy is the most effective approach with excellent results in the management of hemorrhoid disease, but hemorrhoidectomy is not a simple procedure. One of the complications of this surgery is an injury to anal sphincters that can lead to incontinency in some patients. In this study, we aimed to reveal the percentage of external and internal anal sphincter injuries in surgical hemorrhoidectomy. We prospectively enrolled 128 patients from April 2006 to February 2007. They underwent hemorrhoidectomy in three general hospitals in Tehran. All patients were in grade III or IV and underwent open hemorrhoidectomy [Milligan-Morgan]. After surgery, all resected material was histopathologically examined by two expert pathologists and the results confirmed by other one if there is any discrepancy. From all specimens which sent to the pathology department 15.8% [21 Pts.] had muscle fibers that Smooth muscle fibers were seen in 80.5% [17 Pts.] of them and striated muscle fibers were found in 19.5% [4 Pts.]. Although hemorrhoidectomy is a safe and effective method for treatment of hemorrhoid, but the inadvertent removal of smooth and striated muscle during open hemorrhoidectomy had raised concerns about its effects on postoperative anorectal function.

Low diagnostic values of ultrasonography and negative appendectomy: still a major problem in university hospitals

Misdiagnosis of the acute appendicitis may increase the rate of negative appendectomies, which involve a huge waste of resources and are sometimes associated with severe complications. Furthermore, false negative result of ultrasonography [US] could lead to perforation of appendix. Since ultrasonography is still the most common imaging technique used in Iranian appendicitis patients, the study focused on evaluate the accuracy of ultrasonograghy in an educational hospital in Iran. We retrospectively reviewed the results of ultrasonograghy in 270 patients who referred to Rasoul-e-Akram hospital in Tehran, Iran, between April 2002 and October 2004 with acute abdominal symptoms suggestive of appendicitis. The results of ultrasonography were compared with the histopathologic reports of biopsies as a gold standard. In data analysis Chi-square, independent t-test and Mann-Whitney U-test were performed. The accuracy of ultrasonograghy in acute appendicitis was 60.4% and the rate of negative appendectomy was 17.4%. Diagnostic values of US were calculated as the sensitivity of 55.4% [95% confidence interval [CI]=48.6-62], specificity of 72.3% [95%CI=57.1-83.9], positive predictable value [PPV] of 90.4% [95%CI=83.9-94.6] and negative predictable value [NPV] 25.6% [95%CI=18.6-34]. Although the results of our study implied that the diagnostic values of ultrasonography were not considerable, but it is still the only imaging techniques available for patients in Iran. In reference to the low NPV, using an alternative technique such as abdominal CT scan is recommended. More attention must be paid on the signs and symptoms related to acute appendicitis in such patients especially in teaching hospitals