Table 1. Key words used for each layer in the Funnel Model.
| Layer | Content (1998–2017) | Keywords |
|---|---|---|
| Layer 1 | Male Infertility | (A) |
| Layer 2a | Varicocele | (A) AND (Varicocele OR Varicocoele) |
| Layer 2b | Azoospermia | (A) AND (Azoospermia) |
| Layer 2c | Oligozoospermia | (A) AND (Oligozoospermia) |
| Layer 2d | Testicular cancer | (A) AND (Testicular Cancer OR carcinoma) |
| Layer 2e | Erectile Dysfunction | (A) AND (Erectile Dysfunction) |
| Layer 2f | Male Genital Tract infection | (A) AND (Reproductive Tract Infection) |
| Layer 2g | UMI | (A) AND (Unexplained Male Infertility OR Unexplained infertile men OR UMI) |
| Layer 2h | Hypogonadism | (A) AND (Hypogonadism) |
| Layer 2i | Obesity and Metabolic Syndrome | (A) AND (Obesity OR Overweight OR BMI OR Metabolic Syndrome) |
| Layer 2j | Lifestyle | (A) AND (Lifestyle OR Smoking OR Alcohol) |
| Layer 2k | Occupational Exposure | (A) AND (Occupational Exposure) |
| Layer 3 | Mechanistic Studies | (A) AND (Mechanism) |
| Prognostic /Diagnostic Studies | (A) AND (Prognosis OR Diagnosis OR prognostic OR Diagnostic) | |
| Layer 4 | Genomics | (A) AND (Genomics OR Genome) |
| Transcriptomics | (A) AND (Transcriptomics OR Transcriptome) | |
| Proteomics | (A) AND (Proteomics OR Proteome) | |
| Metabolomics | (A) AND (Metabolomics OR Metabolome) | |
| Layer 5 | ART | (A) AND (Assisted Reproductive Technology OR ART OR IVF OR ICSI) |
(A): ALL (Male AND Infertility OR Subfertility OR Sterility) AND (Human OR Man), UMI: unexplained male infertility, BMI: body mass index, ART: assisted reproductive technology, IVF: in vitro fertilization, ICSI: intracytoplasmic sperm injection.