Send letter to journal:
Re: A Time-Lag of Hospital Admission

A Time-Lag of Hospital Admission To the Editor: We read with interest the study by Bell et al,1 who studied the effect of air pollution on the occurrence of pneumonia, ischemic heart disease, and cerebrovascular disease in Taiwan. They analyzed the correlation between the number of patients admitted to National Taiwan University Hospital (NTUH) and some surrogate markers of air-pollution. In the cerebrovascular disease, they claimed that the number of admissions were associated with PM10 and CO, both at a lag of 3 days. It is likely a bias in the representation of the actual number of stroke happened in these period. The NTUH stroke registry initiated in 1995 and is a ongoing stroke registry.2,3 From 1995 to 2006, there were 15196 stroke admissions at NTUH. There are 12624 (83.1%) patients with acute stroke admitted through the emergency department (ED). The average time from the stroke onset to admission was 3.27¡Ó4.71 days (a median of 2 days). Besides, 1609 (12.7%) patients were treated at the ED without admission, and 963 (6.3%) patients had stroke during hospitalization. One study of ED arrival time for acute stroke patients, near one-quarter of stroke patients took more than 24 hours to reach the ED.4 Another study in southern Taiwan, 54% of patient took more than 6 hours from symptom onset to the ED.5 Hence, it is unlikely to represent the actual number of acute cerebrovascular disease by the ICD coding method of hospital admission, and a time lag from the stroke onset to admission occurs frequently. Therefore, the cumulative effect of the pollutants might not be correctly interpreted, and a 3-day lag effect of PM10 and CO toward the cerebrovascular disease might be over -estimated. We suggest that the correlation between the air pollutants and the occurrence of major diseases should be evaluated by the disease onset time, not by the admission time.

Sincerely,

Lung, Chan. M.D., M.Sc. Section of Neurology, Department of Internal Medicine, Far-Eastern Memorial Hospital, Taipei, Taiwan Jiann-Shing Jeng. M.D., Ph.D. Stroke Center and Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan Corresponding to: Jiann-Shing Jeng, MD, PhD Department of Neurology, National Taiwan University Hospital, No 7 Chung- Shan south Road, Taipei 100, Taiwan Tel: +886-2-23123456ext.5338; fax: +886-2-23418395 E-mail address: jsjeng@ntu.edu.tw

References: 1. Bell ML, Levy JK, Lin Z. The effect of sandstorms and air pollution on cause-specific hospital admissions in Taipei, Taiwan. Occup Environ Med 2008;65:104-111. 2. Jeng JS, Lee TK, Chang YC, Huang ZS, Ng SK, Chen RC, Yip PK. Subtypes and case-fatality rates of stroke: a hospital-based stroke registry in Taiwan (SCAN-IV). J Neurol Sci 1998;156:220-226. 3. Yip PK, Jeng JS, Lee TK, Chang YC, Huang ZS, Ng SK, Chen RC. Subtypes of ischemic stroke. A hospital-based stroke registry in Taiwan (SCAN-IV). Stroke 1997;28:2507-2512. 4. Yip PK, Jeng JS, Lu J. Hospital arrival time after onset of different types of stroke in greater Taipei. J Formos Med Assoc 2000;99:532-537. 5. Chang KC, Tseng MC, Tan TY. Prehospital delay after acute stroke in Kaohsiung, Taiwan. Stroke 2004;35:700-704.

Send letter to journal:
Re: Outcome measurement may be misled

The outcome measurement in your study could be very misled. Of the total admissions to National Taiwan University Hospital (NTUH), admissions through the Emergency Department (ED) are only about 40%, which is very low as compared with other hospitals in Taiwan. Most patients presenting to the ED of NTUH with acute ischemic heart disease, respiratory diseases or cerebrovascular disease would not be admitted soon or never admitted. Most admissions to NTUH are reserved for outpatients for elective treatments. I would suggest the authors include the patients in the ED and then analyze the data again.