Howard call together M.D., F.C.C.P...

Howard call together M.D., F.C.C.P.; Charles Feldman, MD FCCP; Howard Sacho, MD; Hermina van der Meuken; Jeremy Kallenbach, MD FCCP; and Hendrik Koornhof, MD

This prospective close attention was undertaken to determine the interpretation of "scanty-positive" acid-fast bacilli forward microscopy and to reevaluate simultaneous microscopy and agriculture of sputum for the accurate diagnosis of pulmonary tuberculosis (PTB) A total of 2560 specimens were proceedinged from 727 patients. There were 435 positive specimens (170 percent) originating from 139 patients, 10 on microscopy only, 176 by refinement only, and 249 on the pair microscopy and culture. Review of the hospital records showed that 107 patients had PTB I had Mycobacterium kansasii colonization, and 31 were consideration not to have PTB. Sensitivity and specificity were 531 and 998 percent for microscopy, 815 and 984 percent for agriculture and 77.6 and 100 percent for microscopy and tillage respectively. Seventy-five microscopy specimens (46 patients) were reported as scanty-positive, of which five (four patients) were thinked false positives, yielding a positive predictive value of 933 percent In those patients with positive sputum microscopy, acid-fast bacilli were descryed in one of the first four specimens. Seven isolates (three patients) were mycobacteria other than tubercle (027 percent of specimens and 16 percent of mycobacteria cultured) Despite the ready availability of laboratory evidence of disease, barely 73 percent of cases were diagnosed by dint of ward staff and 36 percent notified according to the primary physician. Eleven patients (103 percent) died, six of whom had not received diagnoses of PTB before death. Sputum microscopy and improvement remains reliable despite Bayesian predictions when applied to a population with a decreasing incidence of tuberculosis.

(Chest 1989;95:1193-97)

Pulmonary tuberculosis (PTB) remains the major health vexed question in developing countries. This also applies to toward the south Africa, which has a wide gradation of health care facilities.[1] The presumptive diagnosis of active disease hangs on the demonstration of acid-fast bacilli by the agency of microscopy, with definitive diagnosis by means of subsequent culture of Mycobacterium tuberculosis.[2] as well-as; not only-but also; not only-but; not alone-but techniques may be subject to false positive and false negative error. A decreasing reliability of acid-fast bacilli forward smear as a screening experiment for culture-positive pulmonary disease has been predicted as the prevalence of tuberculosis declines (Bayes' theorem). Studies in the United States, India, and Singapore have borne abroad this statistical prediction.[3-5] In view of this, the interpretation of "scanty-positive" specimens has become contentious. This meditation was instituted at Hillbrow Hospital, Johannesburg, to determine the interpretation of scanty-positive microscopy issues and the sensitivity and specificity of Ziehl-Neelsen staining and mycobacterial refinement in a black urban population, since a decline has been reported[6] in the overall prevalence in southward Africa of patients notified of having tuberculosis. Microbiologic investigations were performed prospectively forward all specimens submitted for mycobacterial subject of attention over a 100-day period, and the consequence s were correlated with clinical data.

MATERIAL AND METHODS

A prospective cogitation was undertaken at the Hillbrow Hospital during the 100-day period April 15 to July 25 1986 The mycobacterial proceeds of sputum specimens of adequate convolution and quality that were submitted to the diagnostic laboratories of the southerly African Institute for Medical Research were studied. Specimens were garner uped and submitted by ward staff according to routine practice. Sputum specimens submitted for bacterial refinement were also analyzed for mycobacteria by way of the laboratory.

All technical preparations were carried revealed in a Bio-hazard vertical laminar follow cabinet, Model WVBRS8 (Fibatron Filter Co) which was fitted with prefilters and a high-efficiency particle air filter. Approximately 2 ml of the specimen was transferred to a sterile, 10-ml cork-stoppered glass proof tube and the remainder refrigerated. Laboratory examples were made on unconcentrated specimens.

Smears for Ziehl-Neelsen Staining and Microscopy Preparation

Clean unused glass slides stored in rectified spirits were air dried forward a slide board. Sufficient material was remov from the glass trial tube using a sterile wire loophole and transferred to the glass slide. When the smear had dried sufficiently, it was methanol fixed. Slides were individually transferred to a special staining rack and were always kept apart to interrupt cross-contamination. A 1 percent solution of carbolfuchsin was poured onto the slides and heated in succession a Bunsen burner until steam rose The stain was left in contact with the smear for 10 min; then the stain was washed distant from the slide by a soft stream of filtered water, used for all washing paces The slide was then delugeed for 2 min with a 20 percent aqueous sulphuric acid solution. This additional practice is thought to promote in the decolorization of weakly acid-fast bacteria that are likely to be nonpathogenic. After washing most distant the first decolorizing agent, the slide was flowed with an aliquot of a mixture of 1 ml of concentrated hydrochloric acid and 99 ml of rectified spirits for 5 min. This decolorizing mixture was then washed opposite and the smear counterstained with a 01 percent aqueous methylene melancholy solution for 60 s, and after tender washing the slide was air dried.