to the editor: In Drs. Thaller and Wang's well-written article, “Evaluation of Asymptomatic Microscopic Hematuria in Adults,”¹ some statements regarding the use of radiographic contrast media may be misleading to family physicians. The article states that the incidence of death following this procedure has been reported to be one case per 40,000 administrations. Recent literature indicates that the incidence of fatal reaction might be much lower. A study² involving more than 337,000 patients who were given high-osmolar ionic contrast media or low-osmolar nonionic contrast media revealed no fatalities attributable to the radiographic contrast media. In a meta-analysis³ involving more than 584,000 administrations of high-osmolar ionic or low-osmolar nonionic contrast media, the fatality rate was 0.9 deaths per 100,000 administrations.

Many of the reviewed studies, including the work of Katayama and colleagues,² have been criticized for nonrandom selection. That is, patients with higher risk stratification preferentially received low-osmolar nonionic contrast media. While this is a legitimate criticism of scientific method, it is also a reflection of real world practice and, thus, the statistical yield may reflect the actual risk in a properly screened and treated population. Regardless, numerous reviewers of the data have concluded that because of the extremely low incidence of fatal reaction to radiographic contrast media, studies would have to include several million cases for an accurate determination of the frequency of fatal reaction. In support of Drs. Thaller and Wang,¹ numerous studies do uphold the concept of lower nonfatal, adverse reactions in patients who were administered low-osmolar nonionic contrast media compared with high-osmolar ionic contrast media.

In addition, the authors imply that severe reactions to radiographic contrast media are anaphylactic in nature.¹ In fact, most of the unexpected reactions to this are anaphylactoid. True antigen-antibody mediated anaphylactic reactions to radiographic contrast media are extremely rare: I was able to find only three documented human cases of antibody-mediated adverse reactions.⁴

Finally, no mention was made of the late reactions to radiographic contrast media that are likely to be seen by family physicians. At least one large study⁵ has revealed that late reactions were at least as common as immediate reactions. Fortunately, these reactions were almost invariably self-limited. However, failure to recognize a late reaction could lead to omission of pretreatment or improper risk stratification and, thus, an increased risk of adverse reaction on subsequent radiographic contrast media administration.

to the editor: In their recent review of microscopic hematuria, Drs. Thaller and Wang did a nice job of simplifying a complex subject.¹ However, I believe that their unequivocal recommendation that all patients except children with microscopic hematuria undergo urologic evaluation is controversial. I would like to have seen the authors discuss the alternative approaches. In young adults without risk factors, the incidence of urologic malignancy is quite low. Subjecting all such patients to invasive urologic evaluation may not be in their best interest.

In their recent review of microscopic hematuria, Grossfield and Carroll² discuss the difference in urologic cancer rates between a referral population and a primary care population. Even though they recommend that most patients who are referred to a urologist undergo a thorough evaluation, they acknowledge that a number of sources have questioned the need for cystoscopy in younger patients without risk factors.

Connelly, in Diagnostic Strategies for Common Medical Problems,³ wrote an evidence-based, primary care oriented review of microscopic hematuria. She recommends follow-up observation as the preferred approach for patients who are without risk factors, are asymptomatic and are less than 50 years of age.

The editors of American Family Physician should be applauded for developing the “Problem-Oriented Diagnosis” series. I believe, however, that they should ensure that the recommended diagnostic approaches be based on evidence and when evidence is lacking and controversy exists, it be addressed.

editor's note: These letters were sent to the authors of “Evaluation of Asymptomatic Microscopic Hematuria in Adults,” who did not reply.