{'fraction_non_alphanumeric': 0.018150087260034906, 'fraction_numerical': 0.0017452006980802793, 'mean_word_length': 5.059196617336152, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Critical Elements in Case–Control Studies in Predisposition to Tuberculosis

The reported discrepancy between the Gambian and Croatian population regarding polymorphic IFNGR1 microsatellite and tuberculosis (TB) protection [1] illustrates difficulties in assessing polygenetic susceptibility to a disease, in general. The authors rightly point out additional possibilities for such a result to occur. As the last option, they mention that due to small Croatian population sample, the result might have arisen by chance [2]. Indeed, we wish to extend our studies and get a larger sample size and confirm the result. The reason why our controls were fewer than usual was the following: We believed that the critical element in our case-control study would be the choice of controls. Apart from being unrelated and resembling the patients by ethnicity and age, we opted to put the weight on what we believe is the most important factor, namely, the exposure to the infectious agent. This was carefully observed in our controls, as medical and other personnel working in the Department of Pulmology of the Internal Medicine Division of the regional hospital [1] were the major contributors. However, as it is logically impossible to exclude the possibility that any healthy control would contract tuberculosis in the future, we cannot be absolutely sure that our control group was ideal in this respect. Nevertheless, we believe that the proximity of controls and patients increased the chance for the exposure to the pathogen. We thus hope that our control group might have been enriched for genetically more resistant population that is clearly unrelated to the diseased. Under such circumstances, our controls have a clear advantage over standard ones. The standard control groups are usually chosen by random selection from the pool of blood donors or from persons that are living in the same household with the diseased. The former might never have been in contact with the Mycobacterium tuberculosis. The latter can bias the results if healthy persons living in the same quarters are related even distantly to the diseased, which in turn depends on the cultural and ethnic heritage of the country where the study were performed. Could this be the case with rural population in the Gambia? Perhaps, because of all these factors (and with upscaled sample size), our casecontrol study might stand a better chance of finding differences among genes that might have been previously overlooked. In reported study [1], we did not want to mix standard and selected controls; hence we ended up with a relatively small-sized group. Remedying this would have taken prolonged time on our side. We hoped that reporting it would give more benefits than disadvantages and that it would stimulate discussion about TB susceptibility factors among research groups around the world.