Rationale and objectives-Quadriceps strength relates to exercise capacity and prognosis in chronic obstructive pulmonary disease (COPD). We wished to quantify the prevalence of quadriceps weakness in COPD, and hypothesised that it would not be restricted to patients with severe airflow obstruction or dyspnoea.Methods-Predicted quadriceps strength was calculated using a regression equation (incorporating age, gender, height and fat-free mass), based on measurements from 212 healthy subjects. The prevalence of weakness (defined as observed values 1.645 standardised residuals below predicted) was related to GOLD stage and Medical Research Council (MRC) dyspnoea score in two cohorts of stable COPD outpatients recruited from the United Kingdom (n=240) and the Netherlands (n=351).Main results-32% and 33% of UK and Dutch COPD patients had quadriceps weakness. A significant proportion of patients in GOLD stages 1 and 2, or with an MRC dyspnoea score of 1 or 2, had quadriceps weakness (28% and 26% respectively). These values rose to 38% in GOLD stage 4, and 43% in patients with an MRC Score of 4 or 5.Conclusion-Quadriceps weakness was demonstrable in one-third of COPD patients attending hospital respiratory outpatient services. Quadriceps weakness exists in the absence of severe airflow obstruction or breathlessness.

Letters to the editor/Matters arising arthritis involving I belli and Cryptosporidiunm infestation in patients with AIDS are not yet well known. Further studies should help clarify these questions. We are not aware of any previous report of reactive arthritis after enteric infection due to I belli and we believe this to be the first such report.

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