The current pandemic of COVID-19 is caused by severe acute respiratory syndrome coronavirus-2 (SARS-COV-2) infection. Although clinical data is limited, studies published so far raise concerns about an association between COPD (chronic obstructive pulmonary disease) and worse clinical outcomes in COVID-19. The aim of our study is to determine the association between baseline COPD and outcomes in COVID-19 patients. METHODS: A systematic electronic search was performed in PubMed, Embase, and Google Scholar. Retrospective studies with original hospitalized COVID-19 patient data were included in our study. We used pooled analysis with a random-effects model (Mantel-Haenszel test) to examine the association between COPD and mortality in COVID-19 patients. RESULTS: We analyzed 22 studies from 8 countries that included greater than 11,000 patients. Mean age of the population was 56 and 58% of the population were male. Hypertension was the most prevalent comorbidity in hospitalized COVID-19 patients (42%), followed by diabetes mellitus (23%). COPD was present in 5% of the patients(437/9337) and was associated with higher rates of mortality (OR 3.23, 1.59-6.57; P<0.05). Interestingly, while a 37% of patients(3000/8034) were smokers, smoking was not associated with worsening disease severity (OR 1.52, 0.81-2.87; P=0.20). CONCLUSIONS: Hypertension and diabetes were significantly more prevalent than COPD in these hospitalized COVID-19 patients. While COPD was present in only 5% of included patients, it was associated with higher rates of mortality. While one would expect patients with prior lung disease to have greater mortality with COVID-19, it is curious to see that the prevalence of COPD was lower than the general population (global prevalence is patients>40 years is estimated to be around >9%) and may reflect greater measures taken by COPD patients to avoid coronavirus exposure. Smoking was present in 37% of the patients and interestingly was not associated with higher severity of infection. The reason for this is unclear, More randomized studies are needed to assess the relationship between COPD, smoking status and prognosis in COVID-19 patients. CLINICAL IMPLICATIONS: This will alert clinicians to the worse prognosis of COVID-19 infection in patients with history of COPD and it will raise a question for future studies to look at the association between baseline COPD and COVID-19.

This is a response to the Correspondence from Gabriel Valiente regarding the article "Using Complete K-Trees to Generate Code in Pascal for an Expert System" that appeared in Volume 1 Number 2 of the SIGART Bulletin. Contrary to his assertion that the idea of a complete K-Tree is the central result presented, as the title indicates, the central result is the use of K-Trees to generate high level code for expert systems. Generation of such code is becoming increasingly important as expert systems, or what many people refer to as expert systems, are being integrated into larger applications. We would, nevertheless, like to clarify some of the points made in the Correspondence.

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