# Automatic Extraction of Adverse Drug Reactions from Summary of Product Characteristics
## 2 Materials and Methods
### ADR Extraction
#### 2.3.2 ADR Extraction  
In the previous section, we identify three main structural categories that require different ADR extraction techniques, respectively. An overview of the extraction pipeline for each category is illustrated in Figure 5.  
\begin{table} \begin{tabular}{c c c} \hline \hline
**Term Type** & **Description** & **Examples** \\ \hline \multirow{6}{*}{Frequency} & & Very common \\  & & Common \\  & Terms that describe how often an & Uncommon \\  & ADR happens & Rare \\  & & Very rare \\  & & Not known \\ \hline \multirow{6}{*}{SOC} & & Immune system disorders \\  & & Metabolism and nutrition disorders \\  & & Nervous system disorders \\  & & Eye disorders \\  & The highest level of groupings in & Cardiac disorders \\  & MedDRA. There are 27 groups & Gastrointestinal disorders \\  & which are defined by etiology [9]. & Skin and subcutaneous tissue disorders \\  & & General disorders and administration site \\  & & conditions \\  & Investigations & Investigations \\ \hline \hline \end{tabular}   
* Hyperentially reactions (raath, urticaria, Sleeurs-Johnson Syndrome, angioedema of the skin, Quickke edema, bronchospasm with obstruction, asthma and anaphylaxisacio shock) may occur. * Echinacea can trigger allergic reactions in atopic patients. Association with autoimmune diseases (recognitis desserinata, erythema noosum, immunocompromised/protein, Evans Syndrome, Sleeurs syndrome with renal tubular dysfunction) has been reported. * Leucopenia may occur in long-term use (more than 8 weeks). * The frequency is not known. * If other adverse reactions not mentioned above occur, a doctor or a qualified healthcare practitioner should be consulted. * Reporting suspected adverse reactions after authorisation of the medical product is important. It allows criminal monitoring of the benefits of the medical product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow card Scheme at www.mtr.gov.uk/yellowcard or search for TiffRA Velow Card in the Google Play or Apple Apq. Store. \begin{tabular}{l l l} \hline \hline \multicolumn{3}{c}{**Free-text**} \\ \hline \multicolumn{3}{c}{**Inference system disorders:**} \\ \hline \multicolumn{3}{c}{To uncover the hidden ADRs in the free-text, entity extraction techniques are applied. Specifically, we simplify the extraction process by using the IBM Watson Natural Language Understanding API that offers sophisticated NLP techniques in extracting meta-data from content such as concepts, entities, keywords, and others. Benchmarking studies have shown that IBM Watson Natural Language Understanding API is a simple and useful NLP tool in solving various clinical NLP problems [12; 13]. A demonstration of how the API works is available [14]. Since the number of ADR terms is relatively limited, we can use the API for free. It offers a lite account which can process 30, 000 items per month free of charge [15]. Frequencies of the extracted ADRs are assigned as unknown due to their absence in the free texts. For the structured text, we extract ADR terms and their corresponding frequencies with syntax parsing. The syntactic structure of a structured HTML text is depicted by the occurrences and positions of SOC (System Organ Class) and frequency terms. With the identified positions of SOC and frequency terms, we can obtain the HTML elements that contain only ADR terms. In most cases, ADRs terms in an HTML element are separated by a comma. Thus, by splitting the string by comma, we extract several ADRs for a given SOC and frequency. An example of such ADR extraction is illustrated in Figure 6. The left is the structured text in HTML and the right side shows the extracted ADRs in JSON. The tabular text refers to HTML tables that describe ADRs of a given medicine in a two-dimensional grid format. The first step of information extraction for HTML tables is to detect the structure. As mentioned above, we identify two types of structures: vertical and horizontal.