In the present study, a median of 41 days was encountered between the onset of cough and the initiation of treatment for pulmonary TB in HIV-infected individuals. When this time interval was greater than the median it was assumed that a delay in initiating treatment had taken place and that it was related to the health service.
Comparison of our results with those of others is not straightforward. There is no optimal cut-off point to define delay and the characteristics of the studied populations differ. Our figure (41 days) was higher than those found in studies conducted in a number of countries throughout Asia and Sub-Saharan Africa (ranging from 13-38 days) [8, 14, 16, 17, 24–28], where the median was also the criterion to define health service associated treatment delay, however it was lower than those obtained in Gambia . In a systematic review, the mean delay related to health services in countries with low to moderate financial resources was 28.4 days . There is no basis to judge which of these periods would be acceptable, since a few [17, 27, 29] of the studies evaluated the consequences of the delay on the outcome of TB treatment.
Differences in the population composition regarding the frequency of HIV-infected individuals is also one important factor that may affect comparability between studies. Finnie et al  reported that HIV and its relation with a delay in diagnosing and treating TB was assessed in only 20% of the studies selected for their systematic review. The frequency of HIV-infected individuals in several studies ranged from 16.4% to 67% [14–17], some of which were conducted in countries with a high prevalence of TB/HIV co-infection. Since different criteria were used to define treatment delay it was not possible to compare our findings with those of Kramer  and Hudson , who also focused their studies on HIV-infected patients.
Patients who participated in the present study had regular scheduled consultations before initiating treatment for TB at the two health centers, which are referral centers for treating HIV-infected individuals. It is possible that the differences found in relation to other studies conducted in places with a similar prevalence of TB/HIV co-infection are related to features of the health services and the definition for treatment delay.
The independent factors associated with a delay in the initiation of treatment were: the use of illicit drugs, chest pain, sputum smear-negative and the presence of at least two constitutional symptoms: fever, asthenia and weight loss. There is evidence that intravenous drug users living with HIV, tend to develop TB more than those living with HIV who are not drug users [30, 31]. Nevertheless, drug use has been described as a factor associated with the delayed diagnosis of TB . One explanation for this would be the suppression of the cough reflex as well as the patient’s lack of awareness regarding the cough . This same author suggests that the fear of stigma and the emergence of withdrawal symptoms as the patient comes off the drugs, plus the belief held by health professionals that drug users have poor adherence to long-term treatment, are factors that contribute to a delay in diagnosing TB . It is the belief of this study that the introduction of educational programs for health teams would help to facilitate dialogue with these patients, and that close monitoring would contribute to reducing this delay.
Chest pain is one of the symptoms associated with TB in some studies [18, 19, 33], but no studies have been encountered with an association of diagnostic and treatment delay of TB related to health services. Ngadaya et al  identified that chest pain was associated with the delayed diagnosis of TB, in relation to the patient, since he/she does not attribute sufficient attention to the pain as being a symptom of TB. Chest pain can be attributed to several causes, such as diseases of the pleura, cardiovascular diseases and muscular pain. In a study conducted by our group to diagnose pulmonary TB in HIV-infected individuals with sputum smear negative, no association was revealed between the presence of chest pain and the diagnosis of TB (unpublished data). However, it is necessary to evaluate this information with care, since paying insufficient attention this symptom, although it is correct (as it is associated with the diagnosis), it does not mean that health professionals should exclude the diagnosis of TB when pain is present. Nevertheless, we cannot rule out the possibility that an association between chest pain and delay in the initiation of treatment occurred only by chance.
There was an association of a cough with three constitutional symptoms (referred to in the present study as systemic symptoms) with the delayed initiation of treatment for TB in HIV-infected individuals. These symptoms may be connected to clinical features of other HIV-related illnesses, such as pneumocystis pneumonia or pulmonary fungal diseases, bringing about the need to carry out further investigations into patients, so as to perform a differential diagnosis. It should be noted that the time needed to perform additional tests can play an important role in delayed diagnosis and initiation of TB treatment .
Cain et al. observed in a diagnostic investigation study that the combination of cough with other symptoms (fever or night sweats) increased the sensitivity for diagnosing TB, reaching 93%. However, specificity was low (36%), and thus, the proportion of false positives was high. It is possible that the explanation for findings of this study regarding the presence of constitutional symptoms also explain the findings of these authors. The present study considers that in order to reduce the delay in starting TB treatment in individuals living with HIV, patient surveillance needs to be constant, regardless of the number of potentially TB-associated symptoms, and should be conducted by all health professionals who provide care for HIV-infected patients. The implementation of more rapid diagnostic methods using genetic and semi-automated techniques could also have a positive impact on this problem.
One factor that may limit the interpretation of our findings with regard to clinical symptoms, is that patients in this study were asked about each symptom separately, using a standardized instrument. This fact may have generated a certain degree of disagreement between information obtained by the survey and those obtained by the physician and through medical records.
Sputum smear-negative was found to be associated with a delay in TB treatment, related to health services, both in this study and in a number of others [5, 8, 16, 26, 35].
This fact is of great significance since it is the most widely-used method for diagnosing TB. However, it may fail to detect about 50% of cases of patients with TB/HIV coinfection, due to, amongst other factors, paucibacillary sputum . In the present study, sputum smear-negative was observed in 52% of patients with delayed initiation of treatment, and 22% of the group did not perform a smear test. The CD4 t-cell count, the presence of opportunistic infections and use of ART potentially modify the course and the clinical and radiological features of pulmonary TB , and could be associated with diagnostic and treatment delay of TB. However, no association between these variables and the delayed initiation of treatment was encountered.
The radiological presentation of TB in HIV-infected individuals often progresses with diffuse pulmonary infiltrates or other atypical presentations of TB, a fact that causes the need for differential diagnosis with other respiratory diseases such as pneumocystis, unlike that encountered in immunocompetent patients with TB .
Although it has been reported that the low sensitivity of a chest X-ray may cause a delay in diagnosing TB in HIV-infected individuals , this was not confirmed by the present study.
The present study did not find an association between a delay in treatment for TB and some of the factors described in the literature, such as living in the interior of the state [38, 39], the time taken to travel to a health center, as well as the distance between home and where the patient is attended . It is probable that the findings of this study are due to the fact that all patients were already being attended by referral services, and also because in many cities in the state, local governments provide free transport for patients.
The characteristics of the health service where the study was conducted - with a multidisciplinary team to provide health care for HIV-infected patients (allowing diagnostic investigation of various HIV associated diseases, tuberculosis being one) and with smear and radiological examinations at the unit itself - suggest a potentially lower delay in diagnosing and treating tuberculosis. In Brazil, studies carried out in health services with lower complexity, in the cities of Recife , Victoria  and Rio de Janeiro  indicated among the factors associated with delay, the difficulty in the diagnostic suspicion , limited availability of diagnostic methods  and problems related to the internal organization of the health services . Storla et al. , in a systematic review on this subject, indicated that, regardless of HIV infection, repeated consultations at the same level of care may cause a delay in the diagnosis and treatment of TB.
The characteristics of the population and the complexity of the referral centers involved in this study, should approximate the time delay in the present study to those cited by other Brazilian and international studies. However, some considerations should be taken into account. With the advent of ART, the survival of HIV-infected individuals has increased , thus implying a more complex service for a longer period of time. It is possible that the large numbers of patients attended by these services could cause an overload of pent-up demand on diagnostic resources, besides the difficulty involved in rescheduling missed appointments. The reduced use of culture for diagnosing TB should also be considered, and the method used may cause a delay of up to eight weeks in delivering results. Moreover, the need to use more complex and costly diagnostic methods, especially when the sputum smear is negative, may imply a delay in the diagnosis of TB, as reported in a previous study .
The present study had the advantage of being developed at two referral centers in the state of Pernambuco, attending around 70% of all HIV-infected individuals in the state. One further advantage is the fact that treatment for TB in Brazil is conducted exclusively within the public health service. Drugs for HIV are also distributed throughout the state system. These facts reduce the risk of selection bias.
One limitation of this study is that the differences in the elapsed time between the onset of symptoms and the first consultation could possibly influence the delay time. However, the comparison made between the mean time from the onset of cough to a fresh consultation, according to the different categories of each variable that remained in the final model, showed no statistically significant difference, thus minimizing the possibility of this being an alternative explanation for the findings of this study.