A pilot study of short-duration sputum pretreatment procedures for optimizing smear microscopy for tuberculosis

Performance of Bleach Method Sputum Smear Microscopy for the Diagnosis of Tuberculosis in a Highly Endemic District in Lima, Peru

Background: Sputum smear microscopy (SSM) is a screening test used to diagnose tuberculosis (TB); however, its performance and sensitivity are relatively low, which can lead to false negatives. We designed a cross-sectional study to estimate the performance of SSM that includes a pretreatment based on sputum digestion with bleach (sodium hypochlorite) for the diagnosis of TB. Methods: We evaluated 73 sputum samples from patients with a diagnosis of TB confirmed by the Xpert MTB/RIF test and 114 samples from patients without TB. We performed sputum digestion using a 5% sodium hypochlorite solution, centrifuged at 2000 rpm for 15 min. We prepared smears for direct and bleach-treated SSM and used Ziehl−Neelsen staining. Results: The bleach-treated SSM obtained absolute identification of the cases of TB confirmed by the Xpert test, compared to 95.9% identified by the direct smear method (without bleach treatment). We also found a significant increase (p < 0.001) in the recovery of acid-fast bacilli (AFB) obtained by the bleach-treated SSM (293.8 ± 215.1 AFB) compared to the direct SSM method (222.9 ± 195.5 AFB). The AUC of the bleach-treated SSM and direct SSM was 100% and 96.6%, respectively. Conclusion: The bleach-treated SSM performs better than the direct SSM in identifying AFB and increasing the bacillary count in the sputum samples.

Maximizing microscopy as a diagnostic tool in peripheral health centres of BU endemic areas in Ghana

BACKGROUND

Buruli ulcer (BU) disease, a skin condition caused by Mycobacterium ulcerans (M. ulcerans) is endemic in remote rural areas. Disease diagnosis on clinical basis alone can be misleading, requiring definitive diagnosis based on laboratory tests. Resource constraints in BU endemic areas make microscopy for the detection of acid fast bacilli (AFB) an important and useful method. It is rapid, user-friendly, convenient and cheap. Despite its usefulness, its performance is relatively low. This study investigated modifications of the current method aimed at improving its performance. Forty (IS) 2404 polymerase chain reactions (PCR) positive BU samples were processed by eight physical (centrifugation and overnight sedimentation) and chemical (phenol ammonium sulphate and sodium hypochlorite) modifications of the current direct method. Assessments were based on standard AFB evaluation coupled with in house criteria; positivity (P), clarity and contrast (C) release of bacilli from specimen (R). Overall AFB positivity rate was 64% (409/640). Each protocol had 80 smears. The percentage positivity (P) for the conventional method was 58% (46/80) smears. The highest positivity rate of 57/80 (%) was by protocol 7 (5% phenol in 4% ammonium sulphate (PhAS) and concentrated by overnight gravitational sedimentation). The least positivity rate at 35% (28/80) was by protocol 1 (smears from direct application of swab tips). The differences in performance between the two chemical tested; 5% phenol in 4% ammonium sulphate (PhAS) and 3.5% NaHOCl was significant (p<0.05). The differences between the two physical methods were however not significant (p>0.05). This study concluded that BU samples treated with a solution of 5% phenol in 4% ammonium sulphate and concentrated by either centrifugation or overnight sedimentation is useful for maximizing AFB detection by bright field microscopy. This can be useful in rural health facilities with resource constraints.

Drug resistant strains of Mycobacterium tuberculosis identified through PCR-RFLP from patients of Central Punjab, Pakistan

The study was carried out to determine, by PCR-RFLP, the magnitude of drug resistance in Mycobacterium tuberculosis The study was carried out on 221 random sputum samples collected from patients and 120 suspected cases of drug resistance. Genetic variation in drug-resistant strains was evaluated through PCR-RFLP for isoniazid, ethambutol, streptomycin, and ofloxacin. Out of 341 patients, 91.5% were confirmed as M. tuberculosis complex infected on the basis of PCR. The random samples revealed resistance in 8.2% cases, while 73.3% of those with suspected drug resistance were found resistant. Among drug-resistant isolates, 56.1% were resistant to a single drug, 33.3% to two drugs, and 10.6% to more than two drugs. Ofloxacin resistance was observed along with isoniazid, ethambutol, and streptomycin in 6.5% cases. Resistance to isoniazid was observed in 61% cases, to ethambutol in 50.4%, and to streptomycin in 43.1% cases. It was concluded that PCR-RFLP is a useful molecular technique for the rapid detection of mutations in drug-resistant tuberculosis patients and may be used to diagnose drug resistance at the earliest.

Tuberculosis diagnostics: Challenges and opportunities

Tuberculosis (TB) has been a disease affecting almost all parts of the world since ages. Lot many efforts came in the past for improving diagnosis and treatment. Also, an effective vaccine has been sought after for long. With the emergence of resistant strains of Mycobacterium tuberculosis, the causal organisms of tuberculosis, and complexities emerging due to other associated infections and disease conditions, there is a desperate need for further research input in the field. Be it the better medication and care or better resistance management, proper diagnostics holds the key to success. It has been observed that a high burden of the disease was accompanied by resource limitations and poor research set-up. The scenario remained like this for several decades. With the refreshed vision of resourceful countries and funding agencies, funding is being provided in many areas of research in tuberculosis diagnosis and treatment. This review has been written with an aim to bring forth the limitations of available methods in the field of diagnostics and making researchers aware about the changing scenario with better funding opportunities and support. The author visualizes an enthusiasm from all over the world for the development of better modalities and urges scientists to join the struggle at this very perfect time to take the challenge and come forward with innovations in this field.

Evaluation of two pretreatment methods for the detection of Mycobacterium tuberculosis in suspected pulmonary tuberculosis

The objective of the current study was to compare the efficacy of phenol ammonium sulphate (PhAS) and sodium hypochlorite (NaOCl) pretreatment methods for the direct microscopy with the Löwenstein-Jensen (LJ) culture to detect acid fast bacilli (AFB) from pulmonary tuberculosis suspected cases using sputum specimens. To evaluate PhAS and NaOCl methods, sputum specimens (n = 1145) were studied and the performance of each method was compared with LJ media. The, PhAS centrifuged smear and NaOCl centrifuged smear method demonstrated higher sensitivity (71.47% and 77%), specificity (99.61% and 98%), positive predictive value (98.8% and 94.88%) and negative predictive value (88.35% and 90.25%), respectively, when compared to LJ culture. However, the direct AFB smears and PhAS centrifugation method was ineffective to detect few Mycobacterium tuberculosis cases from sputum specimens, particularly in blood tinged specimens with scanty bacilli. Interestingly, NaOCl method could efficiently detect the Mycobacterium tuberculosis cases from blood tinged sputum specimens with scanty bacilli. The current study concluded that NaOCl method could be the most efficient and sensitive method than direct AFB smear and PhAS centrifuged smear method for the direct detection of AFB in suspected cases of pulmonary tuberculosis.

Evaluation of bleach-sedimentation for sterilising and concentrating Mycobacterium tuberculosis in sputum specimens

Background

Bleach-sedimentation may improve microscopy for diagnosing tuberculosis by sterilising sputum and concentrating Mycobacterium tuberculosis. We studied gravity bleach-sedimentation effects on safety, sensitivity, speed and reliability of smear-microscopy.

Methods

This blinded, controlled study used sputum specimens (n = 72) from tuberculosis patients. Bleach concentrations and exposure times required to sterilise sputum (n = 31) were determined. In the light of these results, the performance of 5 gravity bleach-sedimentation techniques that sterilise sputum specimens (n = 16) were compared. The best-performing of these bleach-sedimentation techniques involved adding 1 volume of 5% bleach to 1 volume of sputum, shaking for 10-minutes, diluting in 8 volumes distilled water and sedimenting overnight before microscopy. This technique was further evaluated by comparing numbers of visible acid-fast bacilli, slide-reading speed and reliability for triplicate smears before versus after bleach-sedimentation of sputum specimens (n = 25). Triplicate smears were made to increase precision and were stained using the Ziehl-Neelsen method.

Results

M. tuberculosis in sputum was successfully sterilised by adding equal volumes of 15% bleach for 1-minute, 6% for 5-minutes or 3% for 20-minutes. Bleach-sedimentation significantly decreased the number of acid-fast bacilli visualised compared with conventional smears (geometric mean of acid-fast bacilli per 100 microscopy fields 166, 95%CI 68-406, versus 346, 95%CI 139-862, respectively; p = 0.02). Bleach-sedimentation diluted paucibacillary specimens less than specimens with higher concentrations of visible acid-fast bacilli (p = 0.02). Smears made from bleach-sedimented sputum were read more rapidly than conventional smears (9.6 versus 11.2 minutes, respectively, p = 0.03). Counting conventional acid-fast bacilli had high reliability (inter-observer agreement, r = 0.991) that was significantly reduced (p = 0.03) by bleach-sedimentation (to r = 0.707) because occasional strongly positive bleach-sedimented smears were misread as negative.

Conclusions

Gravity bleach-sedimentation improved laboratory safety by sterilising sputum but decreased the concentration of acid-fast bacilli visible on microscopy, especially for sputum specimens containing high concentrations of M. tuberculosis. Bleach-sedimentation allowed examination of more of each specimen in the time available but decreased the inter-observer reliability with which slides were read. Thus bleach-sedimentation effects vary depending upon specimen characteristics and whether microscopy was done for a specified time, or until a specified number of microscopy fields had been read. These findings provide an explanation for the contradictory results of previous studies.

Does bleach processing increase the accuracy of sputum smear microscopy for diagnosing pulmonary tuberculosis?

Bleach digestion of sputum prior to smear preparation has been reported to increase the yield of microscopy for diagnosing pulmonary tuberculosis, even in high-HIV-prevalence settings. To determine the diagnostic accuracy of bleach microscopy, we updated a systematic review published in 2006 and applied the Grading of Recommendations Assessment, Development, and Evaluation framework to rate the overall quality of the evidence. We searched multiple databases (as of January 2009) for primary studies in all languages comparing bleach and direct microscopy. We assessed study quality using a validated tool and heterogeneity by standard methods. We used hierarchical summary receiver operating characteristic (HSROC) analysis to calculate summary estimates of diagnostic accuracy and random-effects meta-analysis to pool sensitivity and specificity differences. Of 14 studies (11 papers) included, 9 evaluated bleach centrifugation and 5 evaluated bleach sedimentation. Overall, examination of bleach-processed versus direct smears led to small increases in sensitivity (for bleach centrifugation, 6% [95% confidence interval [CI] = 3 to 10%, P = 0.001]; for bleach sedimentation, 9% [95% CI = 4 to 14%, P = 0.001]) and small decreases in specificity (for bleach centrifugation, -3% [95% CI = -4% to -1%, P = 0.004]; for bleach sedimentation, -2% [95% CI = -5% to 0%, P = 0.05]). Similarly, analysis of HSROC curves suggested little or no improvement in diagnostic accuracy. The quality of evidence was rated very low for both bleach centrifugation and bleach sedimentation. This updated systematic review suggests that the benefits of bleach processing are less than those described previously. Further research should focus on alternative approaches to optimizing smear microscopy, such as light-emitting diode fluorescence microscopy and same-day sputum collection strategies.