Quality assessment of smear microscopy by stratified lot sampling of treatment follow-up slides

SETTING

Ten peripheral laboratories performing routine acid-fast bacilli (AFB) smear microscopy in Lima, Peru.

OBJECTIVES

To test whether external quality assessment (EQA) rechecking of AFB smears becomes more efficient with stratified lot sampling of treatment follow-up smears.

DESIGN

In 2 consecutive years, a stratified lot sample of 36 treatment follow-up slides and 24 diagnostic slides were randomly selected and blindly rechecked. A second controller determined the final result for discordant slides. Feedback was provided to laboratory technicians during supervisory visits.

RESULTS

More false-negative errors were found in the follow-up slides than in the tuberculosis suspect slides: 25 vs. 3. This represented a yield of 3.5% in 720 follow-up slides and only 0.6% in 480 diagnostic slides. Positive predictive values were high in both years. Respectively three and eight laboratories did not reach a relative sensitivity of >65% during the first and second year, and a clear improvement was seen in only one laboratory. Excessive workload seemed to preclude raising the level of routine performance.

CONCLUSIONS

EQA with stratified lot sampling of treatment follow-up slides proved very efficient and effective for identifying laboratories with substandard performance in a setting with low positivity rates in routine diagnostic smears.

A clinical prediction rule for pulmonary tuberculosis in emergency departments

SETTING

University-affiliated hospital located in an area with a high incidence of pulmonary tuberculosis (PTB).

OBJECTIVE

To develop a clinical prediction rule (CPR) based on information obtainable on admission, to permit rapid identification of patients with PTB.

DESIGN

Information from patients with respiratory symptoms who attended the emergency department of Cayetano Heredia Hospital, Lima, Peru, was collected prospectively. Clinical symptoms, past medical history, demographic data and results of chest X-rays (CXRs), sputum smear and culture in Löwenstein-Jensen media were obtained. Based on logistic regression, we constructed a scoring system to predict PTB.

RESULTS

A total of 345 patients were enrolled in the study, including 109 (31%) culture-proven PTB cases. In logistic regression analysis, we found age, previous history of PTB, weight loss, presence of cavities, upper lobe infiltrate and miliary pattern on CXR as independent predictors of PTB. We designed a scoring system with these variables, taking into account their statistical weight. The score attained 93% sensitivity and 42% specificity.

CONCLUSION

The CPR that was developed performed well in our population. It merits further validation in other settings. It should not, however, replace, but should complement sputum microscopy when deciding on isolation, and it does not preclude microbiology in making a definitive diagnosis.

Radical radiation therapy for carcinoma of the prostate in patients with a single hip prosthesis: a technique analysis using dose-volume histograms

Radiation therapy of the prostate patient is sometimes complicated by the presence of a hip prosthesis. Using dose-volume histogram (DVH) data, various techniques were assessed in terms of rectal and bladder sparing, as well as total dose to the femoral head and neck. An attempt was made to isolate a suitable technique in prosthesis patients that was comparable to the standard 4-field box technique in nonprosthesis cases. A 3-field coplanar technique is identified as equally efficacious in terms of rectal sparing, while avoiding the hip prosthesis. The importance of using dose-wall histograms for the rectum in plan ranking is discussed, as are the limitations of DVH data analyses without biological endpoints.

Preoperative radiation therapy to a complex retroperitoneal soft-tissue sarcoma: a case study

Due to their location, retroperitoneal sarcomas tend to present late and with a large size, thus limiting any potential surgical procedure. The inability to achieve local control is the most common cause of treatment failure. This case study describes a challenging example of preoperative radiation therapy for a patient with a retroperitoneal soft-tissue sarcoma. Three-dimensional treatment planning for an asymmetric multibeam arrangement was utilized, with the goal of achieving complete resection at surgery, and thus an improved prognosis, while avoiding high dose to sensitive structures.