Determination of the blood lactate:pyruvate ratio as a noninvasive test for the diagnosis of zidovudine myopathy

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Abstract
Objective. To evaluate the use of the lactate: pyruvate ratio as a test for the detection of zidovudine myopathy.Methods. Twenty consecutive human immunodeficiency virus–infected patients with muscle involvement and 20 without muscle involvement were studied prospectively. Blood lactate and pyruvate levels and serum creatine kinase levels were tested, muscle involvement was assessed both clinically and electrophysiologically, and muscle biopsy was performed in patients with myopathy.Results. Nine patients had biopsy‐proven zidovudine myopathy. All 9 had a high lactate:pyruvate ratio, with elevations on 2 of 2 determinations in 6 patients and on 1 of 2 in 3 patients. Two of 11 patients with other myopathies and 2 of 20 patients without myopathy had a high lactate:pyruvate ratio on 1 of 2 determinations.Conclusion. The lactate:pyruvate ratio, when determined repeatedly, is a sensitive test for detecting mitochondrial muscular toxicity of zidovudine.