Microbiological validation of smear microscopy after sputum digestion with bleach; a step closer to a one-stop diagnosis of pulmonary tuberculosis

Bleach processed smear for Acid fast bacilli staining in Papua New Guinea

The conventional method of processing sputum for acid fast bacilli microscopy has been a primary tool for laboratory diagnosis of pulmonary tuberculosis in Papua New Guinea. In routine preparation, untreated sputum is directly smeared on a glass slide without undergoing any stage of processing. Mounting evidence suggests that direct smearing is less sensitive and, to a certain degree, compromises infection control. A few alternatives for processing sputum have been recommended in the literature; however, their consumables are not easily accessible and are expensive for wide use in rural laboratories. The bleach concentration and processing method appears to be the most preferable choice because bleach is inexpensive, readily available, and has bactericidal properties.

Randomized controlled trial of zinc and vitamin A as co-adjuvants for the treatment of pulmonary tuberculosis

OBJECTIVE

To assess the efficacy of weekly zinc or zinc plus retinol as adjuncts for the treatment of pulmonary tuberculosis.

METHODS

  Double-blind, randomized, placebo-controlled trial in 350 patients >15 years old with smear-positive tuberculosis in Nigeria (ISRCTN36636609). In addition to antituberculous treatment, patients were randomly allocated to weekly supplements of zinc (90 mg), zinc plus retinol (5000 IU) or placebos for 6 months. Primary outcomes were time to sputum smear conversion and resolution of radiographic abnormalities.

RESULTS

After 8 weeks of treatment, 68% had achieved sputum smear conversion, and the median conversion time was 6.5 weeks. Hazard ratios (HR, 95%CI) for sputum conversion relative to the placebo group were not significant for zinc (1.07, 0.92-1.29) or zinc plus retinol (0.89, 0.76-1.07). Significant predictors of time to sputum conversion were lung abnormality score, sputum smear grade, age and serum C-reactive protein. HIV co-infection and gender were not independent predictors of time to sputum conversion. There were no significant differences between supplement groups in clinical, radiological or laboratory outcomes at 2 months or 6 months. There were 9, 9 and 2 deaths in patients receiving zinc, zinc plus retinol or placebos, respectively. Mortality in those who received zinc (HR 1.71, 0.88-3.58) or zinc plus retinol (HR 1.54, 0.78-3.26) did not differ significantly from those who received placebos. Most deaths occurred in patients co-infected with HIV.

CONCLUSIONS

  Supplementation with zinc or zinc plus retinol did not lead to better outcomes than placebos, and caution is warranted regarding routine micronutrient supplementation, particularly in patients co-infected with HIV.

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.

Factors influencing sputum smear conversion at one and two months of tuberculosis treatment

BACKGROUND

In the era of Direct Observation Treatment (DOT) for tuberculosis, clinicians need to focus on high-risk groups. We present sputum conversion rate at one and two months following DOT and its predictors in Oman.

STUDY DESIGN

Hospital-based clinical intervention type of case series.

METHODS

Chest physicians in a referral hospital examined sputum-positive cases of tuberculosis between 2001 and 2006. Patients with HIV infection and treated in the past were excluded. History of smoking, diabetes and duration of symptoms were noted. Sputum was tested for bacillus density. Blood was tested for platelet count and blood sugar levels. One and two months following treatment, the sputum was retested to determine sputum conversion. Regression analysis was done to identify the predictor of late conversion.

RESULTS

Of the 112 sputum-positive TB cases, 39 (34.8%) and 49 (43.7%) cases were sputum negative one and two months respectively after DOT. Lower platelet count was significantly associated with early sputum conversion. (Diff of mean = 38.3 cells x 9/L (95% CI 36.9 - 39.7). On univariate analysis, duration of symptoms, history of diabetes, smoking and ESR were not associated with the early sputum conversion. Knowledge of platelet count seems to assist the clinician to predict the early sputum conversion following DOT for pulmonary TB.

CONCLUSIONS

Sputum conversion rate among tuberculosis patients treated with DOT for one and two months in Oman was 34.8% and 78.6% respectively. Platelet count could assist in predicting early sputum conversion.

Immune parameters as markers of tuberculosis extent of disease and early prediction of anti-tuberculosis chemotherapy response

This study investigates how the extent of pre-treatment radiological disease and early anti-tuberculous treatment response affect levels of selected circulating host immune markers. Twenty HIV-uninfected tuberculosis patients with BACTEC culture positivity for Mycobacterium tuberculosis at diagnosis and treated with directly observed short course anti-tuberculosis chemotherapy and 13 healthy community controls were enrolled. Serum samples were collected throughout treatment. After the intensive phase of treatment, 12 patients remained sputum culture-positive (slow responders) and eight patients were culture negative (fast responders). C-reactive protein (CRP), soluble intercellular adhesion molecule-1 (sICAM-1), soluble urokinase plasminogen activator receptor (suPAR), soluble lymphocyte activation gene-3 (sLAG-3), granzyme B, soluble tumour necrosis factor receptor one and two (sTNFR I and sTNFR II) and soluble death receptor 5 (sDR5) concentrations were measured. High levels of CRP at diagnosis were found to be associated (p</=0.05) with the presence of multiple cavities on chest x-rays and high levels of suPAR and sICAM-1 at diagnosis were associated (p</=0.05) with the extent of alveolar disease. Also significant were the associations between the level of granzyme B (p</=0.01) and LAG-3 (p</=0.05) at diagnosis, and the size of the cavities. The combination of diagnosis and week one measurements of selected serological markers in mathematical models was able to identify the fast responders with up to 87.5% accuracy and the slow responders with up to 83.3% accuracy These preliminary results suggest that predictive models for differential early treatment responses using combinations of host markers hold promise.

Same-day smears in the diagnosis of tuberculosis

OBJECTIVE

To assess the feasibility of completing the diagnosis of tuberculosis (TB) in 1 day by collecting only on-the-spot specimens.

METHODS

Individuals with suspected TB attending district hospitals in Abuja submitted three sputum samples for routine diagnosis (the standard approach). One additional sample was collected 1 h after the first sputum (the same-day approach). One sputum sample was cultured. Blood samples were tested for HIV.

RESULTS

Two hundred and twenty-four patients with chronic cough had 135/672 (20%) positive on-the-spot smears and 47/224 (21%) positive morning smears. The same-day and internationally recommended approaches identified 44 and 45 of the 78 patients with positive cultures, respectively. 106/194 (55%) patients were HIV positive. Only 9-11% of their smears were positive compared with 30-32% for HIV negatives (P < 0.01).

CONCLUSION

It could be possible to diagnose TB in a single day by examining two spot specimens, but the feasibility needs to be confirmed on a larger scale.

Short-term bleach digestion of sputum in the diagnosis of pulmonary tuberculosis in patients co-infected with HIV

The bleach digestion of sputum may improve the yield of smear microscopy but has not been validated in patients with HIV. Therefore we assessed the performance of bleach-digested smear microscopy among patients with HIV. One thousand three hundred and twenty one patients with chronic cough submitted three sputum samples for direct smear microscopy and were offered HIV tests. One sample was selected for a bleach-digested smear and another one was cultured. Patients were classified as having 'definite' (>or=2 positive smears), 'very likely' (smear-negative, culture- positive), 'less likely' (one smear-positive, culture-negative) and 'unlikely' (smear and culture negative) tuberculosis (TB). In all, 566/1045 (54%) patients were HIV positive and 731/1186 (62%) were culture positive. The digested smears were positive in 123/125 (98%) 'definite', 4/118 (3%) 'very likely' and 1/174 'unlikely' TB patients with HIV and in 125/127 (98%) 'definite', 2/74 (3%) 'very likely', 4/4 'less likely' and 2/127 'unlikely' TB without HIV. Three direct smears identified 252 (57%) and one digested smear 254 (57%) of the 444 patients with 'definite' or 'very likely' TB. One bleach-digested smear performed similarly to three direct smears. Both methods were less sensitive in HIV-positive patients. Further studies are needed to compare the performance of the two methods under operational conditions.

Sputum processing methods to improve the sensitivity of smear microscopy for tuberculosis: a systematic review

In low-income and middle-income countries, direct (unconcentrated) sputum smear microscopy is the primary method for diagnosing pulmonary tuberculosis. The method is fast, inexpensive, and specific for Mycobacterium tuberculosis in high incidence areas. The main limitations of direct microscopy are its relatively low sensitivity, especially in individuals co-infected with HIV, and variable quality of the test in programme conditions. Thus, there is a need to identify methods to improve the sensitivity of microscopy. Physical and chemical sputum processing methods, including centrifugation, sedimentation, and bleach, have been studied and found to show promise. We did a systematic review to assess the ability of different processing methods to improve the sensitivity of microscopy. By searching many sources, we identified 83 studies. Overall, by comparison with direct smears, the results suggested that centrifugation with any of several chemical methods (including bleach) is more sensitive, that overnight sedimentation preceded by chemical processing is more sensitive, and that specificity is similar. There were insufficient data to determine the value of sputum processing methods in patients with HIV infection. Operational studies are needed to determine whether the increased sensitivity provided by processing methods is sufficient to offset their increased cost, complexity, and potential biohazards, and to examine their feasibility.