Risk Factors for Smear Negative And Culture Positive Results Among Pulmonary Tuberculosis Patients in Mwanza, Tanzania

Abstract

Background: Smear negative and culture positive results in pulmonary tuberculosis are not uncommon yet the underlying factors are not well established. Objective: To determine factors associated with smear negative and culture positive results. Methods: Pulmonary tuberculosis patients were consecutively recruited for 12 months from five health facilities in Mwanza region, Tanzania. Sputum examinations were done at the recruitment centre and at the TB reference laboratory using Auramine O technique. Culture was done at the TB reference laboratory using Lowenstein Jensen solid media. A post-hoc analysis compared patients who had a smear negative culture positive result (case) with patients who had not (controls). Results: A total of 655 pulmonary TB patients were recruited, 18 had no culture results and were excluded from the analysis. Of the remaining 637 patients, 127 (19.9%) had three negative smears at the recruitment centre and 34 patients were a case. Current smoking was strongly associated with being a case, especially in women. Of the 127 patients who had three negative smears at the recruitment center, 104 (81.9%) also had a negative smear at the reference laboratory. Of these, 13 (12.5%) were still culture positive. Conclusion:The frequencies of smear-negative culture-positive results differ between health facilities, indicating possible difference in quality of laboratory procedures. Strengthening of laboratory capacity is needed both for optimizing smear microscopy techniques, and for performing sputum cultures for diagnosing TB when there is a high rate of suspicion. The association between smoking and smear negative culture positive TB needs to be assessed in adequately large studies.

Prevalence of tuberculosis, multidrug resistant tuberculosis and associated risk factors among smear negative presumptive pulmonary tuberculosis patients in Addis Ababa, Ethiopia

“…Different risk factors have different impacts on the occurrence and diagnosis of SNPT. Studies have shown different risk factors for the occurrence of SNPT [9, 24, 25]. But, there is limited information about factors associated with SNPT in the study area.…”

Evaluation of Smear Negative Pulmonary Tuberculosis Before and After Antibiotic Use: The Case of Four Public Health Centers of Addis Ababa, Ethiopia

“…Higher prevalence of smear negative culture positive PTB saw in a study conducted in Ethiopia at St. Peter TB specialized Hospital, 43/247 (17.4%) patients whose smears negative for acid-fast bacilli found to be positive for mycobacterial culture [9]. Similarly, higher prevalence of (17.5%), (26.8% ) and (27.8%) smear negative culture positive results seen in Kenya, Tanzania and Peru respectively [10][11][12]. The variation of prevalence of SNPT may be a due difference of study population, the status of the patient and method of diagnosis.…”

“…A presumptive diagnosis of AFB sputum smear-negative PTB was made in 41.8% (173) of all study subjects, and patients started on anti-TB treatment as recommended by the Tanzania NTLP. The remaining 58.2% (240) patients were assumed to have other forms of respiratory diseases and were treated accordingly [11].…”

Evaluation of the Same Day Diagnosis of TB Microscopy in Comparison with Spot-Morning-Spot Method in Selected Public Health Institutions, Addis Ababa, Ethiopia

“…The sensitivity of this method varies and depends upon the collection of sufficient sputum, proper preparation of smears, good staining technique, careful examination of smears, and availability of a good microscope. Several methods have been tried to improve smear microscopy for AFB [3]. On the other hand, Light Emitting Diode (LED) microscopes are less expensive, require less power and are able to run on batteries, the bulbs have a very long halflife.…”