To the Editor: 

I read with interest the report by Draisci et al.  on the prevalence of latex allergy in obstetrical patients.1Although there was a statistical difference between the obstetrical patients (OB) and the nonobstetrical women (non-OB), I must disagree with the author's conclusion that the results prove that higher prevalence is due to the factor of pregnancy alone.

Unfortunately, the two groups were not matched for risk factors. As noted in the same issue of ANESTHESIOLOGY, Sampathi and Lerman described the risk factors for developing latex allergy: congenital abnormalities (spina bifida, genitourinary abnormalities), multiple surgeries, atopy to drugs or food, exposure to latex, and healthcare worker.2 

In table 1, Draisci et al.  list the prevalence of latex sensitization and the risk factor prevalence. The authors did not find a statistical difference for risk factors between the two groups (OB and non-OB). But if one looks closer, one would see that there might be a difference that could result in the difference in latex sensitization found.

In absolute numbers, the OB group had 15 patients who were positive for latex sensitization, whereas the non-OB group had 5 such patients, with both groups having 294 patients in each. In other words, the OB group had 10 more patients who tested positive for latex allergy than did the non-OB. Looking at the risk factors listed, one finds that the OB group had six to seven more patients with positive results than did the non-OB: specifically, drug allergy (atopy), seven more; food allergy (atopy), six more; other allergy (atopy), seven more; multiple surgeries, six more; and healthcare workers, six more. If this difference of six to seven patients accounts for the majority of difference in latex sensitization, the findings of higher prevalence in the OB group is because of the higher prevalence of risk factors.

Unfortunately, the authors do not discuss this confounding issue in their report. Thus, I must conclude that the authors did not have enough evidence to make the conclusion that pregnancy is a risk factor for latex allergy.

Draisci G, Zanfini BA, Nucera E, Catarci S, Sangregorio R, Schiavino D, Mannocci A, Patriarca G: Latex sensitization: A special risk for the obstetric population? ANESTHESIOLOGY 2011; 114:565–9
Sampathi V, Lerman J: Perioperative latex allergy in children. ANESTHESIOLOGY 2011; 114:673–80