To the Editor:  

I would like to voice my reservations concerning the famous 1920 article by R. Kendrick Smith, MD, DO,¹ that reported the success of the osteopathic approach to the influenza pandemic of 1918. 

In medical school and in various professional lectures I have attended, Dr Smith's article¹ has been touted as near-certain evidence that one of the mechanisms of osteopathic manipulative treatment (OMT) is the stimulation of lymphatic flow, implying the provocation of improved immune function. In his report,¹ Dr Smith's basic tenet was that the stimulation of immunity through OMT saved lives in the face of a tragic event—the influenza pandemic of 1918 (ie, “Spanish flu”)—for which there was no cure. 

The 1920 article, as published in JAOA—The Journal of the American Osteopathic Association,¹ was derived from a lecture delivered at the Annual Convention of the American Association of Clinical Research in October 1919. The article has many problems when evaluated by today's rigorous standards for epidemiologic research. 

The etiologic agent of the 1918 influenza pandemic was an orthomyxovirus designated as H1N1. At the time of the pandemic, however, there was little (if any) understanding of viruses. In fact, it was widely believed that Pfeiffer's bacillus (a gram-negative bacterium now known as Haemophilus influenzae) was the etiologic agent.² Without the correct pathogen identified, an accurate diagnosis of the disease could not be made. Modern investigations of outbreaks in which firm diagnosis cannot be made are typically classified into likelihood of disease (ie, definite, probable, and possible cases), and analyses are made based on these classifications. Dr Smith¹ does not mention how the diagnoses of influenza were confirmed in the cases he cites. He also fails to mention if the patients were categorized by probability of disease based on symptoms for analysis. 

The influenza pandemic of 1918 was characterized by three distinct waves of disease in the United States. The first wave of the pandemic took place in the spring, the second wave occurred in the fall, and the final wave took place during the winter and extended into early 1919.³ The virulence of the disease in the spring of 1918 was rather mild when compared with the two subsequent waves. After some moderate antigenic drift, early exposure to the virus in the spring seemed to confer some protective effects when the virus reappeared in subsequent seasons.³ Dr Smith¹ does not note which wave(s) infected the patients in his report. Nor does he comment on the history of his patients vis-à-vis the early semiprotective spring exposure. I believe these omissions may represent a noteworthy confounding factor. 

Yearly influenza is notable for increases in mortality at the extremes of age. The 1918 influenza pandemic, however, produced its greatest mortality among individuals whose ages ranged from 20 to 40 years.⁴ It has been postulated that individuals who were older than 40 years may have been exposed to an earlier influenza strain that conferred partial immunity against the pandemic 1918 strain, resulting in a lower risk of mortality for that demographic group.⁵ In his article, Dr Smith¹ does not mention patient age. Theoretically, osteopathic physicians practicing in 1918 and 1919 could have been treating mainly older patients who previously received partial immunoprotection from earlier influenza strains while allopathic physicians may have had a greater proportion of patients who were younger and had not received such immunoprotection. It is possible that this is one explanation for the different mortality rates of patients treated by osteopathic versus allopathic physicians. 

The details of the data-accumulation process used by the AOA to study the 1918 influenza pandemic may have been lost to time. Dr Smith¹ reported that 2445 osteopathic physicians responded to a request for information on the pandemic that the AOA sent to all members. From these 2445 osteopathic physicians, the AOA received “authenticated detailed case reports” for “110,120 cases of influenza with only 257 deaths.”¹ These numbers are the origin of the oft-quoted “one-quarter of 1%” mortality rate for patients with influenza who were treated osteopathically during the 1918 pandemic. Current, more rigorous scientific methods dictate that pooling data from multiple physicians without predetermined standards—let alone a clear mechanism for diagnosing the disease in question—would make for inaccurate data. 

The conclusions drawn from Dr Smith's observations,¹ though intriguing, can be explained by the confounding factors I have detailed above. I would like to propose that the methods used in the original AOA report be determined and published. The publication of this information would have medical and historic merit. Furthermore, I believe that the AOA's data from the 1918 pandemic should be reanalyzed by today's more stringent statistical methods—that is, if the data can be found. Until then, I believe that we need to consider the “one-quarter of 1%” statistic an interesting, though mainly anecdotal, historic observation. 

Currently, most public health authorities believe that another influenza pandemic is inevitable.⁶ Remaining unknown, however, is the influenza strain or subtype that will be responsible for this pandemic—and, of course, the event's timing. The most likely candidate for pandemic potential in the near future remains the avian influenza strain H5N1 (ie, “bird flu”).^6,7 

Thus, appreciating that the study published by Dr Smith¹ is critically flawed, and by way of preparing for the possible pandemic outbreak of H5N1.^6,7 

I challenge the osteopathic research community to initiate protocols necessary to begin studying the effects of OMT in patients who are exposed to or infected with H5N1. Nothing would vindicate the observations of our osteopathic predecessors better than replicating studies of H1N1 under similar conditions (should we be able to determine them) and getting similar results for H5N1. 

Because of the lack of scientific standards for Dr Smith's now 88-year-old editorial,¹ I believe that it is our responsibility as a profession to stop referring to it as though it remains a work with scientific merit. I recently refereed a research proposal that cited Dr Smith's article¹ as a legitimate piece of scientific research. After brief reflection, I realized that I, too, was guilty of citing Dr Smith's work,¹ in an article that was published in 2000.⁸ So, if I could modify the statement that I originally made in that article: 

 

I would reword the statement as follows: