title: Substandard tuberculosis drugs on the global market and their simple detection.
abstract: METHODS
  The prevalence of substandard anti-tuberculosis drugs is unknown. To maximize the effectiveness of tuberculosis (TB) control efforts, simple, inexpensive drug quality screening methods are needed.
  
  
  METHODS
  Isoniazid (INH) and rifampin (RMP) single- and fixed-dose combination (FDC) formulations were collected from selected TB programs and pharmacies in Colombia, Estonia, India, Latvia, Russia and Vietnam. Samples were screened using a recently developed thin-layer chromatography (TLC) kit. All abnormal samples and a 40% random sample of normal formulations were further analyzed using confirmatory techniques. Samples outside of 85% to 115% of stated content, and/or containing compounds other than the stated drug, were defined as being substandard.
  
  
  RESULTS
  Overall, 10% (4/40) of all samples, including 13% (4/30) RMP samples, contained <85% of stated content. More FDCs (5/24, 21%) than single-drug samples (2/16, 13%) were substandard. A comparison of TLC with the confirmatory analysis for RMP analysis showed a sensitivity of 100% (4/4), a specificity of 92% (24/26), a positive predictive value (PPV) of 67% (4/6), and a negative predictive value (NPV) of 100% (24/24). An analysis of INH showed a specificity of 90% (9/10). However, sensitivity, PPV, and NVP could not be determined.
  
  
  CONCLUSIONS
  A substantial number of anti-tuberculosis drugs from several countries, in particular FDCs, were found to be substandard. Such drugs may contribute to the creation of drug-resistant TB. TLC is an effective, convenient, and inexpensive method for the detection of substandard drugs.
authors.affiliation: Division of TB Elimination, National Centers for HIV/AIDS, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. kel4@cdc.gov
authors.forename: K F
authors.initials: KF
authors.lastname: Laserson
authors.forename: A S
authors.initials: AS
authors.lastname: Kenyon
authors.forename: T A
authors.initials: TA
authors.lastname: Kenyon
authors.forename: T
authors.initials: T
authors.lastname: Layloff
authors.forename: N J
authors.initials: NJ
authors.lastname: Binkin
mesh_terms: D000995:Antitubercular Agents / Q000032:analysis* / Q000592:standards; D001208:Asia; D002855:Chromatography, Thin Layer / Q000379:methods*; D003105:Colombia; D004338:Drug Combinations; D005061:Europe, Eastern; D006801:Humans; D007538:Isoniazid / Q000032:analysis* / Q000592:standards; D011237:Predictive Value of Tests; D011786:Quality Control; D012015:Reference Standards; D012293:Rifampin / Q000032:analysis* / Q000592:standards; D012680:Sensitivity and Specificity; D014376:Tuberculosis / Q000188:drug therapy*
chemical_list: D000995:Antitubercular Agents; D004338:Drug Combinations; D007538:Isoniazid; D012293:Rifampin