Determination of iron by the Ferrochem II: Interference by tuberculostatics

Abstract

San José M E, Sarandeses A, Alvarez D, Valdes L, Chomón B, del Rio M J. Determination of iron by the Ferrochem II: interference by tuberculostatics. Scand J Clin Lab Invest 1993; 53: 653-658.

Iron levels in samples from certain treated tuberculous patients are underestimated by the Ferrochem II analyser. Of the tuberculostatic drugs examined for a possible interference, isoniazid, ethambutol, rifampicin, pyrazinamide and Rifater® (a mixture of rifampicin, isoniazid and pyrazinamide), only pyrazinamide and Rifater® (due to its pyrazinamide content) were associated with iron levels differing significantly (p < 0.001) from those of controls, with means of –317.2 and – 185.6μnoll⁻¹ for pyrazinamide and Rifater® respectively as against 9.91 μmoll⁻¹ for the controls. The negative interference (I) due to pyrazinamide was independent of iron level in the samples but dependent on pyrazinamide concentration in the same (P) (r = 0.9993), I = –0.4380P -0.4276.

Key Words:

• analytical interference
• ethambutol
• iron
• isoniazid
• pyrazinamide
• rifampicin
• tuberculosis