Strengths and limitations of assessing influenza vaccine effectiveness using routinely collected, passive surveillance data in Ontario, Canada, 2007 to 2012: balancing efficiency versus quality.

Prompt evaluation of annual influenza vaccine effectiveness (IVE) is important. IVE is estimated in Ontario using a test-negative design (TND) within a national sentinel surveillance network (SPSN). To explore alternative approaches, we applied the screening method (SM) during five seasons spanning 2007 to 2012 to passive surveillance data to determine whether routinely collected data could provide unbiased IVE estimates. Age-adjusted SM-IVE estimates, excluding 2008/09 pandemic cases and cases with missing immunisation status, were compared with TND-IVE estimates in SPSN participants, adjusted for age, comorbidity, week of illness onset and interval to specimen collection. In four seasons, including the 2009 pandemic, the SM underestimated IVE (22­39% seasonal; 72% pandemic) by 20 to 35% relative to the TND-IVE (58­63% seasonal; 93% pandemic), except for the 2010/11 season when both estimates were low (33% and 30%, respectively). Half of the cases in the routine surveillance data lacked immunisation information; imputing all to be unimmunised better aligned SM-IVE with TND-IVE, instead overestimating in four seasons by 4 to 29%. While the SM approach applied to routine data may offer the advantage of timeliness, ease and efficiency, methodological issues related to completeness of vaccine information and/or case ascertainment may constitute trade-offs in reliability.

Intellectual impairment in chronic renal failure.

In a dialysis centre with a high tap water aluminium content and a known high incidence of dialysis encephalopathy, 29 patients undertaking regular home dialysis, without clinical evidence of encephalopathy, were studied with a battery of psychological tests that have proved useful in detecting early organic intellectual deterioration in other conditions. Full-scale intelligence quotient, as measured by the Wechsler Adult Intelligence Scale, did not differ significantly from that of the normal population, but the patients showed significant deficiencies in three tests of performance--namely, digit symbol, block design, and picture arrangement. The ability to acquire new information in relation to performance was impaired and the abnormality increased with time on dialysis. Such tests should be useful in early detection of dialysis dementia at a reversible stage.

A method for measuring human behavioural and physiological responses at different stress levels in a driving simulator.

1. A method is described by which a car simulator can be used to measure, simultaneously, motor-perceptual performance and physiological responses of human subjects under different levels of task difficulty or stress.2. Motor-perceptual performance was measured in terms of reaction times taken by subjects to carry out steering, braking and operation of traffic indicators in the simulator. Subjects were instructed to carry out the different driving manoeuvres by means of a command panel containing five coloured lights. Three levels of task difficulty or stress were devised. In level 1 only the light signals were used. In level 2 the driving simulator film was shown and all of the light signals reinforced the movements of the car in the film. Level 3 was similar to level 2, with the exception that whilst some of the light signals reinforced the movements of the car, others deliberately conflicted with it.3. Physiological responses measured were heart rate, blood pressure, respiration and calf blood flow. Personality was also measured by means of the Cattell 16 personality factor questionnaire.4. Analysis of variance of the performance of 15 subjects showed significant variation between the three task levels (P=<0.001 for steering reaction times; P=<0.01 for brake and indicator reaction times). In all cases the reaction times were longest for level 3, indicating that this was the most difficult task. The number of anticipated responses to steering, braking and traffic indicator signals was highest in level 2, while the number of corrections to steering and braking responses was lowest in level 2. None of these differences was statistically significant.5. Of the physiological variables, the heart rate showed a progressive increase from task levels 1 to 3 but only those between levels 1 and 3 were statistically significant (P<0.05).6. The results are discussed in relation to the validity of the method. It is concluded that by means of this method it is possible to produce controlled and reproducible degrees of stress and under conditions which are also suitable for the investigation of pharmacological agents upon it.

The effects of cigarette smoking on the response to stress in a driving simulator.

1. Some behavioural and physiological responses of cigarette smokers and non-smokers exposed to varying degrees of stress in a driving simulator were compared.2. When the smokers were smoking a cigarette, some of their reaction times to light signals differed significantly from those of non-smokers, some being longer and some shorter. These differences disappeared when the smokers were not smoking.3. Of the physiological measurements, only heart rate differed significantly between smokers and non-smokers, being higher at all levels of stress in the smokers. There were no significant differences in blood pressure, calf blood flow and respiration rate between smokers and non-smokers.4. The results of the Cattell Sixteen Personality Factor Questionnaire showed that the smokers were significantly more extroverted and self-reliant than the non-smokers.5. The results are discussed in relation to the pharmacology of cigarette smoking. It is concluded that the differences in reaction times and heart rates between smokers and non-smokers were a consequence of cigarette smoking.