To the Editor:
Tinea capitis (TC), a scalp and hair dermatophytosis, is a common childhood infection.1 US data on the species causing TC are geographically limited or outdated.1–4 We aimed to describe TC testing practices and causative organisms to improve clinical management.
We analyzed Labcorp (a major US commercial laboratory) data sent to Centers for Disease Control and Prevention’s National Syndromic Surveillance Program, a collaborative electronic health data sharing effort among Centers for Disease Control and Prevention, health departments, and academic and private sector partners. We identified fungal culture results ordered during March 1, 2019 to October 31, 2022 using Logical Observation Identifiers Names and Codes codes and patients with suspected TC using International Classification of Diseases, 10th Revision code B35.0. We examined patient demographic characteristics, ordering clinical specialty, species, and order month.
Among 20,259 fungal culture results, most patients were children (median age: 8.0 years, interquartile range: 5.0–14.0), male (53.5%), and Southern US-based (65.3%) (Table I). The most common ordering specialties were dermatology (43.3%) and pediatrics (35.6%).
Table I.
Fungal culture results from persons with suspected tinea capitis in a large national commercial laboratory dataset—United States, March 1, 2019 to October 31, 2022*
| Feature | n = 20,259 | % |
|---|---|---|
|
| ||
| Median age in years (IQR) (n = 20,209) | 8.0 | (5.0–14.0) |
| Sex (n = 20,001) | ||
| Female | 9304 | 46.5 |
| Male | 10,697 | 53.5 |
| US census region (n = 20,253) | ||
| Midwest | 938 | 4.6 |
| Northeast | 4779 | 23.6 |
| South | 13,218 | 65.3 |
| West | 1318 | 6.5 |
| Provider type (n = 17,060) | ||
| Dermatology | 7393 | 43.3 |
| Pediatrics | 6074 | 35.6 |
| Family, general practice, internal medicine | 2238 | 13.1 |
| Other | 1355 | 7.9 |
| Fungal culture result | ||
| Negative/no fungal growth | 13,213 | 65.2 |
| Positive for fungus† | 7046 | 34.8 |
| Dermatophytes | 4864 | 69.0 |
| Trichophyton | 4336 | 89.1 |
| T. tonsurans | 2914 | 67.2 |
| T. violaceum | 135 | 3.1 |
| T. rubrum | 98 | 2.3 |
| T. mentagrophytes | 68 | 1.6 |
| T. soudanense | 30 | 0.7 |
| Other Trichophyton species‡ | 10 | 0.2 |
| Unspecified Trichophyton species | 1081 | 24.9 |
| Other dermatophytes | 528 | 10.9 |
| Microsporum | 517 | 97.9 |
| M. canus | 477 | 92.3 |
| M. gypseum | 24 | 4.6 |
| M. audouinii | 16 | 3.1 |
| Epidermophyton | 11 | 2.1 |
| Nondermatophyte molds | 804 | 11.4 |
| Dematiacious molds | 476 | 59.2 |
| Aspergillus species | 83 | 10.3 |
| Fusarium species | 47 | 5.8 |
| Other | 198 | 24.6 |
| Yeasts | 763 | 10.8 |
| Candida species | 342 | 44.8 |
| Unspecified yeast | 270 | 35.4 |
| Rhodotorula species | 108 | 14.2 |
| Trichosporon species§ | 10 | 1.3 |
| Other | 33 | 4.3 |
| Unspecified fungus | 615 | 8.7 |
This period represents the widest range of available data. We used the following Logical Observation Identifiers Names and Codes codes to identify fungal cultures: 17947–3, 17948–1, 17949–9, 18482–0, 42804–5, 42805–2, and 51723–5.
Approximately 4.3% of fungal culture results had >1 species identified; however, data on combinations of species could not be obtained at the time of analysis.
Other Trichophyton species included T. verrucosum and T. interdigitale.
Trichosporon species included T. asahii, T. inkin, and T. mucoides.
Overall, 7046 (34.8%) results were positive for fungus; of these, 69.0% were dermatophytes, 11.4% nondermatophyte molds, 10.8% yeasts, and 8.7% unspecified fungus. Among dermatophytes, 89.1% were Trichophyton (89.5% T. tonsurans [among those identified to species level]), 10.6% Microsporum (92.3% M. canus), and 0.2% Epidermophyton.
Overall, fungal culture results from children aged 3 to 12 years, males, Midwesterners, and specimens ordered by nondermatologists had the highest percent positivity and, among positives, highest frequency of dermatophytes (Table II). Fewer dermatology results were from 3- to 12-year-olds (46.5%) versuss other specialties (range: 64.2%–72.3%). The monthly number of culture results declined 48.1% from March 2020 to April 2020, remaining generally lower thereafter, with relatively consistent percent positivity (Supplementary Material, available via Mendeley at https://doi.org/10.17632/rxzzct2g56.1).
Table II.
Fungal culture results from persons with suspected tinea capitis in a large national commercial laboratory dataset, by result—United States, March 1, 2019 to October 31, 2022*
| All results | Dermatophytes | Nondermatophyte molds | Yeasts | Unspecified fungus | |
|---|---|---|---|---|---|
|
|
|
||||
| Feature | No. positive/No. tested (%) | No. (%), among positive results | |||
|
| |||||
| Age group, years (n = 20,209) | |||||
| 0–2 | 686/2051 (33.4) | 474 (69.1) | 88 (12.8) | 80 (11.7) | 44 (6.4) |
| 3–12 | 5285/12,188 (43.4) | 3992 (75.5) | 456 (8.6) | 423 (8.0) | 414 (7.8) |
| 13–21 | 428/2437 (17.6) | 201 (47.0) | 73 (17.1) | 107 (25) | 47 (11.0) |
| >21 | 638/3533 (18.1) | 193 (30.3) | 187 (29.3) | 149 (23.4) | 109 (17.1) |
| Sex (n = 20,001) | |||||
| Male | 4273/10,697 (39.9) | 3098 (72.5) | 446 (10.4) | 412 (9.6) | 317 (7.4) |
| Female | 2694/9304 (29.0) | 1718 (63.8) | 345 (12.8) | 338 (12.5) | 293 (10.9) |
| US census region (n = 20,253) | |||||
| South | 4548/13,218 (34.4) | 3026 (66.5) | 573 (12.6) | 473 (10.4) | 476 (10.5) |
| Northeast | 1693/4779 (35.4) | 1250 (73.8) | 148 (8.7) | 221 (13.1) | 74 (4.4) |
| West | 413/1318 (31.3) | 289 (70.0) | 45 (10.9) | 45 (10.9) | 34 (8.2) |
| Midwest | 389/938 (41.5) | 297 (76.3) | 38 (9.8) | 24 (6.2) | 30 (7.7) |
| Provider type (n = 17,060) | |||||
| Dermatology | 2147/7393 (29.0) | 1272 (59.2) | 351 (16.3) | 297 (13.8) | 227 (10.6) |
| Pediatrics | 2341/6074 (38.5) | 1735 (74.1) | 223 (9.5) | 242 (10.3) | 141 (6) |
| Family, general practice, internal medicine | 880/2238 (39.3) | 620 (70.5) | 92 (10.5) | 74 (8.4) | 94 (10.7) |
| Other | 553/1355 (40.8) | 414 (74.9) | 48 (8.7) | 48 (8.7) | 43 (7.8) |
| Total | 7046/20,259 (34.8) | 4864 (69.0) | 804 (11.4) | 763 (10.8) | 615 (8.7) |
This period represents the widest range of available data.
Our analysis found a higher combined percentage of yeasts and nondermatophyte molds (>20%) compared with data from a 1990s to 2000s US multicenter survey (<5.5%).4 These organisms likely represent scalp or hair colonization or contamination and, unlike TC, rarely require systemic antifungal treatment. Consistent with other US studies, T. tonsurans was the most common dermatophyte.1 Microsporum prevalence was relatively high compared with previous studies (10.6% vs 0%–10.3%).1,3,4 Notably, terbinafine, often chosen for TC therapy because of its shorter duration, is less effective than griseofulvin against Microsporum.5 The lower percent positivity among specimens from dermatologists might reflect more comprehensive testing, including in age groups with lower TC prevalence. Decreased in-person school attendance and care-seeking during the COVID-19 pandemic might explain the decline in fungal cultures after March 2020. The low percent positivity (34.8%) in this study is similar to results from Foster et al4 (range: 33.1%–52.3%). This might reflect the insensitivity of fungal cultures for dermatophytosis or other conditions (eg, seborrheic dermatitis, psoriasis) that clinically resemble TC.
Limitations include that the dataset is not nationally representative and lacked information on underlying conditions, race/ethnicity, and testing besides cultures (eg, antifungal susceptibility). Also, because International Classification of Diseases, 10th Revision code B35 can represent TC or tinea barbae, some specimens from older patients might not represent suspected TC.
In sum, our study provides updated TC epidemiologic data and highlights the importance of laboratory testing to confirm suspected TC and ensure correct diagnosis and treatment.
Footnotes
Conflicts of interest
Dr Lipner has served as a consultant for BelleTorus Corporation, Ortho-dermatologics, Moberg Pharmaceuticals, and Hoth Therapeutics. Dr Gold, Author Benedict, and Dr Lockhart have no conflicts of interest to declare.
IRB approval status: Not applicable.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.
This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy (eg, 45 C.F.R. part 46, 21 C.F.R. part 56; 42 U.S.C. §241(d); 5 U.S.C. §552a; 44 U.S.C. §3501 et seq).
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