Extrapulmonary involvement associated with Mycoplasma pneumoniae infection.

Mycoplasma pneumoniae infection usually presents with upper and lower respiratory tract infection. Extrapulmonary involvement is not uncommon, however. We report two cases of predominantly extrapulmonary manifestations of Mycoplasma pneumoniae infection without significant pulmonary involvement. Both cases were diagnosed by serology. These cases illustrate the diversity of clinical presentations of Mycoplasma pneumoniae infection. Clinicians should maintain a high index of suspicion.

The first novel influenza A (H1N1) fatality despite antiviral treatment and extracorporeal membrane oxygenation in Hong Kong.

We report the first fatality caused by novel influenza A (H1N1) infection despite having the diagnosis confirmed and being given antiviral treatment after hospitalisation. This patient was also the first with influenza A (H1N1) to be supported with extracorporeal membrane oxygenation in Hong Kong. Although extracorporeal membrane oxygenation is an effective means of supporting patients with refractory hypoxaemia on high mechanical ventilatory support, it is labour-intensive and technically demanding. We also discuss the challenges faced when managing this case.

Conditional local influence in case-weights linear regression.

The local influence approach proposed by Cook (1986) makes use of the normal curvature and the direction achieving the maximum curvature to assess the local influence of minor perturbation of statistical models. When the approach is applied to the linear regression model, the result provides information concerning the data structure different from that contributed by Cook's distance. One of the main advantages of the local influence approach is its ability to handle the simultaneous effect of several cases, namely, the ability to address the problem of 'masking'. However, Lawrance (1995) points out that there are two notions of 'masking' effects, the joint influence and the conditional influence, which are distinct in nature. The normal curvature and the direction of maximum curvature are capable of addressing effects under the category of joint influences but not conditional influences. We construct a new measure to define and detect conditional local influences and use the linear regression model for illustration. Several reported data sets are used to demonstrate that new information can be revealed by this proposed measure.

A local influence approach to identifying multiple multivariate outliers.

We make use of Cook's local influence approach and its recent modification by Poon and Poon to develop measures for detecting multivariate outliers. The motivation and the foundation of the theory are geometrical and are different from classical approaches; however, whilst the proposed measure exhibits a form similar to those in the literature, it still has a considerable advantage in having transformed the classical measures to the unit interval. The new approach unifies outlier identification measures using geometrical concepts. It involves no distributional assumption or large-sample properties, and allows the flexibility of identifying outliers with respect to different metrics. The approach therefore provides a valid reason for using the various measures in complicated situations, such as in non-normal cases and in small-sample problems.

Acute renal failure in a healthy young adult after dextran 40 infusion for external-ear reattachment surgery.

Dextran 40 is used to improve the microcirculation after certain surgical procedures. We report a rare case of acute anuric renal failure in a healthy young adult after administration of dextran 40 to improve the microcirculation following ear-reattachment surgery. The renal failure was subsequently reversed by plasmapheresis and intensive care support. Although rare in the young and fit, the risk of developing acute anuric renal failure exists with administration of dextran 40 and appropriate monitoring is essential.