LAUSR

In their recent article, Kulchavenya et al. described the clinical spectrum and characteristic features of a cohort of 142 patients with urogenital tuberculosis (UGTB) [1]. Based on their observations, they concluded “identification of mycobacterium tuberculosis (Mtb) in modern UGTB is difficult. Therefore, the most advanced microbiological technology should be used to establish the correct diagnosis.” Although the diagnostic modalities for Mtb have undergone rapid changes over time, the identification of bacilli in urine continues to be Achilles heel of many of these investigations [2–5]. In this series, Kulchavenya et al. have rightly pointed out this important aspect of the difficulty in managing UGTB. However, the study gives rise to certain questions which we thought would be worth sharing. The authors have described in their methods that “early morning specimens of urine were cultured for Mtb as well as for non-specific microflora.” However, they have not mentioned how many early morning specimens were taken from each patient. This is an important cause of discrepancy in the detection rates of many diagnostic modalities, specifically in Mtb, as being a paucibacillary disease; the more the number of samples, the more will be the detection rate. While routine screening microscopy is done on an average of three to five early morning samples, many a time when it comes to culture or GeneXpert MTB/RIF (GeneXpert), a single or at most two samples are taken [5–9]. In a recent meta-analysis for checking the diagnostic accuracy of nucleic acid amplification tests (NAATs) in urine for genitourinary tuberculosis, in only three out of 11 studies that were selected for analysis, three morning urine samples were analyzed with the rest being done with single sample [9]. Although most of the studies showed good sensitivity inspite of a single sample being taken, whether this high sensitivity can be reproducible in all centers is questionable. In the center, it was noticed that many suspected UGTB patients who had positive smears on microscopy had negative results in GeneXpert. When it was further probed into this discordance, it was come to know that most of the time the centers where the samples for GeneXpert are taken did not insist on early morning samples and unlike routine examination; only one sample was taken. Another question that arises is as follows: was a preliminary screening microscopy done before culture in all these patients and if so, what was its positivity rate. Although historically the sensitivity of microscopy is less, still they have been extrapolated mostly, from series of pulmonary tuberculosis on sputum samples, as modern series on UGTB are still very less in literature. Large studies like these can throw light on the detection rate of microscopy and correlation with culture and Gene expert specifically in urine. Lastly, according to Pang et al. compared with the high viscosity of sputum samples, the urine specimens are more homogeneous. Hence, they hypothesized that using the same treatment process that is used in sputum can be too rigorous for urine and that due to the overexposure to the extreme alkaline environment of tubercle bacilli in the urine samples, a large percentage of Mtb gets inactivated, thereby resulting in the low recovery rate by conventional culture method This comment refers to the article available online at https ://doi. org/10.1007/s0034 5-019-02767 -x.