This was a prospective cross-sectional descriptive study including both descriptive and analytical components.

The study was conducted at the Renaissance University Hospital Center in N’Djamena, Chad, a tertiary referral hospital with a dedicated otorhinolaryngology department. Data collection was carried out over an 18-month period, from July 1, 2022 to December 31, 2023.

The study population consisted of patients aged 3 years and older who presented with acute pharyngitis to the otorhinolaryngology department of the Renaissance University Hospital Center during the study period.

Patients aged 3 years and older presenting with acute pharyngitis were included after receiving information about the study and providing consent.

Patients with complicated pharyngitis, those who had received prior antibiotic therapy, and patients or legal guardians who declined participation were not included.

All included patients underwent a systematic clinical examination performed by the consulting clinician. The McIsaac score, validated for patients aged 3 years and older, was calculated during the consultation. The score is based on five clinical criteria (fever >38˚C, absence of cough, tender anterior cervical lymphadenopathy, tonsillar hypertrophy or exudate, and age) and ranges from −1 to 5, with higher scores indicating a greater probability of group A streptococcal infection.

The rapid antigen detection test (RADT) for group A streptococcal pharyngitis was continuously available throughout the study period. It was an immunochromatographic qualitative test detecting group A streptococcal antigen from a pharyngeal swab.

RADT was performed systematically in children aged 3 to 15 years. In adolescents and adults (≥16 years), RADT was recommended when the McIsaac score was ≥3; however, due to a high clinical workload and organizational constraints related to patient flow, the test could not be performed systematically in all eligible patients. RADT was not performed in patients with a McIsaac score <3. Each test included an internal control band and was used in accordance with the manufacturer’s recommendations.

During the study period, rapid antigen detection tests were provided free of charge to patients as part of routine hospital care, ensuring that economic barriers did not influence test utilization.

Pharyngeal sampling was performed using a sterile swab rubbed over both tonsils and the posterior pharyngeal wall, avoiding contact with adjacent oral structures. Results were obtained after an approximate reading time of 5 minutes and interpreted by the clinician based on the presence of test and control bands.

RADT sampling and interpretation were performed by the attending physicians of the otorhinolaryngology department, all of whom received standardized training on RADT procedures prior to the start of the study.

Data were collected prospectively using a standardized data collection form completed by the consulting clinician. Collected variables included sociodemographic characteristics, clinical findings, McIsaac score, performance and result of RADT, and antibiotic prescription.

Data were analyzed using the Statistical Package for the Social Sciences (SPSS), version 26.0. Descriptive and analytical analyses were performed to assess the association between the McIsaac score and RADT results, as well as between RADT results and antibiotic prescription. Pearson’s chi-square test or Fisher’s exact test was used as appropriate, with statistical significance set at p < 0.05.

The study was conducted in accordance with ethical principles for health research. Participation was voluntary after appropriate information. For patients under 18 years of age, parental or guardian consent was required. Anonymity and confidentiality of data were strictly ensured.

A total of 136 patients aged between 3 and 67 years were included in the study. The mean age was 19.8 ± 13.2 years. The 3 - 15-year age group was the most represented, with 69 patients (50.7%), followed by the 16 - 28-year group (33 patients; 24.3%) and the 29 - 41-year group (24 patients; 17.6%).

There were 71 females (52.2%) and 65 males (47.8%), yielding a male-to-female ratio of 0.92.

The distribution of patients according to age and sex is presented in Table 1.

Table 1. Distribution of patients by age group and sex (n = 136).

Percentages by sex were calculated within each age group.

The McIsaac score ranged from 1 to 5. Score 4 was the most frequently observed, recorded in 52 patients (38.2%), followed by score 3 in 28 patients (20.6%). The detailed distribution of McIsaac scores is shown in Table 2.

Table 2. Distribution of patients according to McIsaac score (n = 136).

The rapid antigen detection test (RADT) was performed in 91 patients, representing 66.9% of the total study population (91/136).

All patients aged 3 - 15 years underwent RADT (69/69). Among patients aged 16 years and older (n = 67), RADT was performed in 22 patients (32.4%), while 45 patients (67.6%) were not tested. This included 16 adults with a McIsaac score of 3 who were eligible for testing but did not undergo RADT due to logistical and organizational constraints.

The distribution of RADT performance according to age group is presented in Table 3.

Table 3. Performance of RADT according to age group (n = 136).

Percentages were calculated by row.

Among the 91 patients who underwent RADT, the test was positive in 65 patients (71.4%) and negative in 26 patients (28.6%).

Most RADT-positive results were observed in children aged 3 - 15 years, accounting for 56 cases.

The distribution of RADT results by age group is presented in Table 4.

RADT positivity was significantly more frequent in patients aged 3 - 15 years compared with those aged 16 years and older (Fisher’s exact test, p < 0.01) (Table 5).

Table 4. RADT results according to age group (n = 91).

Table 5. Association between age group and RADT result (n = 91).

Statistical test: Fisher’s exact test; p < 0.01. Percentages were calculated by row.

Among the 91 tested patients, RADT positivity increased with higher McIsaac scores. RADT was positive in 25.0% of patients with a score of 3, 75.0% with a score of 4, and 85.2% with a score of 5.

Table 6. Association between McIsaac score and RADT result among tested patients (n = 91).

Statistical test: Fisher’s exact test; p < 0.05. RADT positive and negative percentages were calculated by row. Percentages in the “Total” column were calculated based on tested patients (n = 91).

Statistical analysis showed a significant association between McIsaac score and RADT result (Fisher’s exact test, p < 0.05). Detailed results are shown in Table 6.

Among the 91 patients who underwent RADT, antibiotic therapy was prescribed in 69 patients (75.8%).

All patients with a positive RADT result (65/65) received antibiotic treatment. Among patients with a negative RADT result, antibiotics were prescribed in 4 cases (15.4%), while 22 patients (84.6%) did not receive antibiotic therapy. Among the RADT-negative patients who received antibiotics, severe clinical signs were observed, including persistent high fever, marked tonsillar inflammation, or significant cervical lymphadenopathy.

Statistical analysis using Fisher’s exact test demonstrated a highly significant association between RADT result and antibiotic prescription (p < 0.001). The relationship between RADT result and antibiotic prescription is presented in Table 7.

Table 7. Association between RADT result and antibiotic prescription (n = 91).

Statistical test: Fisher’s exact test; p < 0.001. Percentages were calculated by row.

The study population was predominantly young, with a majority of patients aged 3 - 15 years, accounting for more than half of the included cases. This age distribution is consistent with international data showing that acute pharyngitis, particularly streptococcal pharyngitis, primarily affects school-aged children and adolescents [4][12].

The near-equal sex ratio observed in our series is also comparable to that reported in other clinical and epidemiological studies, suggesting no marked sex-related difference in the occurrence of acute pharyngitis [1][8].

The McIsaac score is a validated clinical tool used to estimate the probability of streptococcal pharyngitis and to guide diagnostic strategies [5][6]. In our study, high scores (4 and 5) were frequently observed, reflecting a strong initial clinical suspicion of bacterial infection.

However, the association between the McIsaac score and RADT results showed that, despite a statistically significant correlation, some patients with high clinical scores had negative RADT results. This finding is consistent with previous studies indicating that clinical scores, while useful for triage, are insufficient on their own to reliably confirm group A streptococcal infection [2][6][13]. The McIsaac score should therefore be regarded as a tool for clinical orientation rather than a definitive diagnostic test.

In our series, RADT was positive in 71.4% of tested patients. This relatively high positivity rate should be interpreted with caution. It is largely explained by the targeted testing strategy adopted, based on strict clinical criteria, particularly among adolescents and adults, in whom RADT was performed only when the McIsaac score was ≥3.

This approach introduces a selection bias, as RADT was not performed in all patients presenting with acute pharyngitis, especially among those aged 16 years and older with low clinical scores. Consequently, the proportion of RADT-positive results among tested patients does not reflect the true prevalence of streptococcal pharyngitis in the overall study population.

Moreover, in the absence of microbiological culture as a reference standard, our study does not allow assessment of the sensitivity or specificity of RADT. Rather, it primarily evaluates the practical usefulness of RADT in clinical decision-making, rather than its intrinsic diagnostic performance, as emphasized in previous methodological studies [9][14][15].

One of the major findings of this study is the highly significant association between RADT results and antibiotic prescription. All patients with a positive RADT received antibiotic therapy, whereas most patients with a negative RADT did not.

These results indicate that RADT contributed to better alignment between therapeutic decisions and objective diagnostic evidence, thereby limiting unnecessary antibiotic prescriptions. This observation is consistent with numerous studies demonstrating that integrating RADT into the management of acute pharyngitis significantly reduces inappropriate antibiotic use [3][8][14].

In a context marked by the growing burden of antimicrobial resistance, particularly in sub-Saharan Africa, this impact represents an important public health benefit [7][16].

In sub-Saharan Africa, the management of acute pharyngitis often relies solely on clinical assessment, due to limited access to microbiological investigations and organizational constraints within health systems [10][11]. Several African studies have reported a tendency toward antibiotic overprescription for upper respiratory tract infections, contributing to the emergence of bacterial resistance [16]-[18].

Our study demonstrates that the rational use of RADT is feasible in an African tertiary hospital and may contribute to improving the quality of care for patients with acute pharyngitis. These local data support international recommendations advocating for simple, accessible diagnostic strategies to combat antimicrobial resistance [7][9][19].

This study has several limitations. Its single-center design may limit the generalizability of the findings to other healthcare settings. In addition, the lack of microbiological confirmation by culture prevents assessment of the diagnostic accuracy of RADT in our context.

Furthermore, in children, asymptomatic carriage of group A streptococcus—well documented in the literature—may lead to a positive RADT result in the absence of active infection, representing a recognized limitation of rapid antigen tests [12][20]. Nevertheless, the prospective nature of data collection, the use of standardized clinical criteria, and appropriate statistical analyses strengthen the validity of the observed results.