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Accurate diagnostic tests have a key role in patient management and the control of most infectious diseases. Unfortunately, in many developing countries, clinical care is often critically compromised by the lack of regulatory controls on the quality of these tests. The information available on the performance of a diagnostic test can be biased or flawed because of failings in the design of the studies which assessed the performance characteristics of the test. As a result, diagnostic tests are sold and used in much of the developing world without evidence of effectiveness. Misdiagnosis leading to failure to treat a serious infection or wasting expensive treatment on people who are not infected remains a serious obstacle to health.

BACKGROUND: Outbreaks of respiratory tract infections are common in long-term care facilities for older people. The objective of our study was to determine both the frequency of such outbreaks and their clinical and epidemiological features. METHODS: Prospective surveillance for outbreaks of respiratory tract infections and a retrospective audit of surveillance records were conducted in 5 nursing homes in metropolitan Toronto over 3 years. The clinical manifestations of infected residents were identified and microbiological investigations for causal agents were conducted. RESULTS: Sixteen outbreaks, involving 480 of 1313 residents, were identified prospectively during 1 144 208 resident-days of surveillance, for an overall rate of 0.42 infections per 1000 resident-days. Another 30 outbreaks, involving 388 residents, were identified retrospectively. Outbreaks occurred year-round, with no seasonal pattern. Pathogens included influenza virus, parainfluenza virus, respiratory syncytial virus, Legionella sainthelensi and Chlamydia pneumoniae. Multiple pathogens were detected in 38% (6/16) of the prospectively identified outbreaks. Of the 480 residents in the prospectively identified outbreaks 398 (83%) had a cough, 194 (40%) had fever and 215 (45%) had coryza. Clinical findings were nonspecific and could not be used to distinguish between causal agents. Pneumonia developed in 72 (15%) of the 480 residents, and 58 (12%) required transfer to hospital. The case-fatality rate was 8% (37/480). INTERPRETATION: Our findings emphasize the importance of adequate surveillance for outbreaks of respiratory tract infections in nursing homes and of early diagnosis so that appropriate interventions can be promptly instituted.

OBJECTIVE: To determine whether serologic evidence of Chlamydia trachomatis during pregnancy is a risk factor for preterm delivery (before 37 weeks' gestation). DESIGN: Chart review. SETTING: Antenatal clinics associated with a teaching hospital. PATIENTS: A group of 103 unselected consecutive patients presenting for routine prenatal care. OUTCOME MEASURES: Pregnancy outcome and C. trachomatis serologic status. RESULTS: A total of 21 women (20%) were found to be seropositive for IgG antibodies to C. trachomatis. They were similar to the seronegative women with respect to maternal age, parity, history of preterm birth, obstetric or medical problems, smoking status, history of drug abuse, educational status and psychosocial stressors. The seropositive women were significantly more likely than the seronegative women to have a preterm birth (24% [5/21] v. 7% [6/82]i p = 0.029, odds ratio 3.96, 95% confidence interval 1.08 to 14.57), an infant with a lower mean gestational age at birth (262 [standard deviation (SD) 19] days v. 273 [SD 15] days; p = 0.0052) and an infant with a lower mean birth weight (3125 [SD 692] g v. 3473 [SD 696] g; p = 0.0434). The positive predictive value of a seropositive result for preterm birth was 31% (5/16); the negative predictive value of a seronegative result for preterm birth was 8% (6/76). CONCLUSION: Women with serologic evidence of C. trachomatis may be at risk for preterm birth. Further study is required to determine whether serologic testing for C. trachomatis should be a routine part of prenatal care.