PAs challenge study findings

The American Academy of Physician Assistants (AAPA) and the Society of Dermatology Physician Assistants (SDPA) issued a statement challenging the results of an analysis published in the April 18 issue of JAMA Dermatology by Anderson, et al.

The article, “Accuracy of Skin Cancer Diagnosis by Physician Assistants Compared with Dermatologists in a Large Health Care System,” is a medical record review of 33,647 skin cancer screening examinations on 20,270 patients (64.9%) who were treated at a single center between Jan. 1, 2011 – Dec. 31, 2015.

The AAPA and SDPA question the use of the “number needed to biopsy (NNB)” ratio which was used to determine diagnostic accuracy. NNB is controversial ― even among dermatologists, they stated. In August 2016, Michael A. Marchetti, M.D., et al., wrote in JAMA Dermatology: “Considering NNB without attention to the sensitivity applied to the detection of skin cancer and the prevalence of skin cancer could prove misleading.”

The study found that to diagnose one case of skin cancer, the NNB was 3.9 for PAs and 3.3 for dermatologists.  Per diagnosed melanoma, the NNB was 39.4 for PAs and 25.4 for dermatologists. Patients screened by a PA were significantly less likely than those screened by a dermatologist to be diagnosed with melanoma in situ, but differences were not significant for invasive melanoma or nonmelanoma skin cancer, which is a telling point, according to the AAPA and SDPA.

“The inherent trade-off between sensitivity and specificity dictates that 2 clinicians with identical diagnostic accuracy but with different thresholds of sensitivity for their examinations will have discordant NNBs, as graphically illustrated by receiver operating characteristic curves,” Marchetti et al. write.

The article is not representative of the quality of care provided by PAs, said L. Gail Curtis, PA-C, MPAS, DFAAPA, president and chair of the American Academy of Physician Assistants board of directors. Learn more  about the response from the Academy of Physician Assistants (AAPA) and the Society of Dermatology Physician Assistants (SDPA)

During the study period, 30 clinicians (15 dermatologists and 15 PAs) provided skin cancer screening, which in itself is potentially problematic due to the small size, AAPA and SDPA contends. It is “fundamentally flawed with too small a sample size to be representative of the PA profession,” they stated in a joint statement.

“While the article states that the 15 PAs saw a higher percentage of people with a history of skin cancer, the dermatologists saw more patients with a history of melanoma. We would expect a higher rate of melanoma diagnosis in this patient population. Also, these patients with a history of melanoma could be choosing to see the dermatologist over the PA. In the same vein, people who seek removal of a non-cancerous skin lesion for cosmetic or convenience reasons (e.g. a mole irritated by clothing) may choose to see the PA (for ease of getting an appointment), rather than the dermatologist; and the universal standard of care is to send the sample for biopsy, even if there is no concern that skin cancer exists,” states the AAPA and SDPA.

“There is no way to fully separate the decision making of the PA from the decision making of the physician because in this case, the physician assistant must have supervisory agreement by a physician.

“PAs value sustained partnerships with physicians, have great respect for the depth of physician training, and rely on the PA/physician team in clinical practice,” said Jane Mast, PA-C, MPAS, SDPA president. “There is a wealth of research that highlights improved patient outcomes from the high-quality care that PAs provide. We welcome further research into PAs in dermatology.”

REFERENCES
Ayce M. Anderson, PhD; Martha Matsumoto, MD; Melissa I. Saul, MS; et al.  “Accuracy of skin cancer diagnosis by physician assistants compared with dermatologists in a large health care system,” JAMA Dermatology. April 18, 2018. DOI:10.1001/jamadermatol.2018.0212
Michael A. Marchetti, MD; Stephen W. Dusza, DrPH; Allan C. Halpern, MD. “A Closer Inspection of the Number Needed to Biopsy,” JAMA Dermatology, August 2016. DOI:10.1001/jamadermatol.2016.0936