To the Editor:-Asirvatham et al. [1] reported a case of "prolonged loss of consciousness and elevated porphyrins following propofol administration." In view of this, the authors conclude that it might be the first report to doubt whether propofol, an agent considered to be safe in porphyric patients, is indeed safe. However, we doubt the diagnosis of porphyria in this case and, therefore, doubt the conclusion.

To the best of our knowledge, increases in urinary aminolevulinic acid, porphobilinogen, and coproporphyrin III are not necessarily compatible with the diagnosis of coproporphyria, a diagnosis suggested by the authors. These biochemical findings may be compatible with any type of neurogenic porphyria (coproporhyria, acute intermittent, variegate) as a primary cause and also may reflect secondary changes due to other clinical states (e.g., liver injury, effect of drugs, lead poisoning). [2,3] Various biochemical tests, related to porphyrin biosynthetic pathway, conducted in the urine, feces, and blood may indicate which of the aforementioned causes leads to the abnormalities reported in the urine. [4] According to the case report, none of these tests was performed. The diagnosis of coproporhyria, for example, should be based on disturbed fecal porphyrin profile with elevated coproporphyrin that predominates and a reversed ratio of coproporphyrin III/I (from < 1 in normal patients to up to 30 in coproporphyric patients). [5,6] To complete the diagnosis, the activity of lymphocyte coproporphyrinogen oxidase may be determined. [2] The test, which is accurate and reliable, is being conducted in a few porphyria reference laboratories. Both tests are used to establish a diagnosis also in the latent phase and may therefore be performed in the patient after recovery.

We suggest that the patient be checked by a reference laboratory authorized for the biochemical diagnosis of porphyria before any conclusion concerning the use of propofol in porphyric patients is drawn.

In addition, we would like to point out a few mistakes in the report of the biochemical findings in the urine: aminolevulinic acid and porphobilinogen are not porphyrins but precursors in the porphyrin biosynthetic pathway; the excretion of aminolevulinic acid and porphobilinogen is determined in micromoles per 24 h and that of porphyrins in nanomoles per 24 h, not in millimoles as reported in the article.

Rivka Mamet, Ph.D.

Nili Schoenfeld, Ph.D.

Porphyria Reference Laboratory; Rabin Medical Center, Beilinson Campus; Petah-Tikva, Israel

(Accepted for publication March 23, 1999.)

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