The Z-score: A new tool in the interpretation of spirometric data.

Spirometry is an important tool in the diagnosis and management of patients with respiratory pathology. An appropriate interpretation of the spirometric data requires the use of a population-specific reference equation. However, the most widely used equations were established in European populations with limited age groups. The extrapolation of these equations, based on a specific population, and their uses for a different population led to measurement and interpretation biases. In 2012, an international working group conducted a multicenter study and published new reference equations called The Global Lung Initiative (GLI). These enabled the modeling of spirometric parameters from a very large sample collected in several ethnic groups using modern statistical techniques to establish continuous equations for all ages and in many countries. The GLI also recommends the use of a new statistical tool for the expression of results: The Z-score. This tool allows to express, in a simple way: how many standard deviations a subject is deviated from its reference value. The Z-score is calculated by the ratio of the difference between the measured value and that predicted with the residual standard deviation. This simple approach has reduced the false positive results found by the use of the conventional limits of 80% compared to a predicted value or 0.70 in absolute value for the definition of bronchial obstruction that remain still used.

Preoperative assessment in pulmonary resection surgery.

Pulmonary resection can be associated with a significant risk of morbidity and mortality, which depends on the nature and extent of pulmonary resection but also on the patient himself. This risk can be apprehended by a preoperative assessment which estimates the immediate operative risk as well as the physiological state and the post-operative quality of life which can require more conservative therapies. Currently, preoperative exploration of a patient is based on various technological tools, which can range from simple electrocardiogram or simple spirometry to a complex exploration such as a cardiorespiratory effort test. These multiple evaluation tools require the rationalization of good practice processes according to international recommendations, taking into account the patient's specificity and the country context. This approach makes it possible to prioritize examinations according to their availability and accessibility in order to identify patients with high operative risk and to offer them an appropriate therapeutic choice.