Predictive Score of Boonsarngsuk et al for Identifying a Patient in Thailand with Drug-Resistant Tuberculosis

 

Patient selection: Thai with tuberculosis that has been previously treated

 

Goal: identify a patient with either isoniazid or rifempicin resistant tuberculosis

 

Parameters:

(1) chest radiograph appearance

(2) relapse following previous treatment

(3) adequacy of previous antituberculosis treatment

Parameter	Finding	Points
chest radiograph appearance	normal or mildly advanced	0
	moderately advanced	1
	far advanced	3
relapse after prior therapy	> 6 months	2
	<= 6 months	5
adequacy of previous therapy	complete	0
	incomplete	4

 

total score =

= SUM(points for all 3 factors)

 

Interpretation:

• minimum score: 2

• maximum score: 12

• A score >= 3 yielded the least error in identifying drug-resistant vs drug-susceptible disease.

• Since the minimum score is 2, the score becomes positive if any of the parameters is positive. The only person not identified as being at risk is someone who relapsed more than 6 months after completing the drug regimen and who has a normal or mildly abnormal chest X-ray.

 

Performance:

• The sensitivity was 58% and specificity 68%, indicating a relatively poor test.

• The negative predictive value was 94%. while the positive predictive value was 15%

• Prevalence of drug-resistant strains would be important in test performance.

 

Limitations:

• The score may perform differently in different populations.

• Adequacy of the regimen (use of appropriate antituberculous drugs) is another factor to consider.

• Exposure to someone with drug-resistant tuberculosis or acquisition of infection in an area with high resistance might be added to the score.

• Multi-drug resistance may be of more concern.