Research design

This study was a retrospective cohort study to compare the clinical and economic effects of Gastrodin injection and Extract of Ginkgo Biloba Leaves injection for hospitalization patients diagnosed with dizziness or vertigo (see STROBE checklist in Additional file 1).

Composition information

In 1980, the chemical synthesis of Gastrodin was completed. The State Medicine Administrative Bureau approved Gastrodin injection of China as a new drug and first authorized the KPC Pharmaceuticals, Inc to manufacture in 1984. At present, 25 pharmaceutical companies are producing Gastrodin injection, with 37 approvals (including different specifications).

Botanical

Gastrodia elata Blume (Orchidaceae) is an obligate mycoheterotrophic plant, an orchid popularly used in traditional Chinese medicine [40]. It is primarily found in China, Nepal, Bhutan, India, Japan, North Korea, Siberia, and Taiwan [41, 42]. In China, it grows mainly in Sichuan, Yunnan, Guizhou, and Hunan Province [43], where can provide high-quality daodi medicinal products [44]. Gastrodia elata Blume is cited by the Pharmacopoeia of China [45] and has been used in oriental medicine in East Asia to treat various diseases, including neurological disorders as an anticonvulsant, analgesic, and sedative medication [46].

Chemical

Gastrodin injection is a kind of traditional Chinese medicine injection that is extracted and refined from G. elate [28]. The main ingredient is gastrodin and identified by the State Medicine Administrative Bureau of China. Since the early 1950s, China has begun to study the chemical composition of gastrodin. Nearly 100 compounds have been isolated from gastrodin. In 1978, gastrodin was isolated from the ethanolic extract of Rhizoma Gastrodiae for the first time [47, 48]. Through silica gel colum chromatography, 14 gastrodin compounds have been isolated and identified, included 8 phenolic components were fractionated: 4-hydroxybenzaldehyde (4-HBAL), 4-hydroxybenzyl alcohol (4-HBA), benzyl alcohol, bis-(4-hydroxyphenyl) methane, 4-(4/-hydroxybenzyloxy) benzyl methylether, 4-hydroxy-3-methoxybenzyl alcohol (vanillyl alcohol), 4-hydroxy-3-methoxybenzaldehyde (vanillin), and 4-hydroxy-3-methoxybenzoic acid (vanillic acid) [46, 49].

Target population and data source

The target population of this study included inpatients whose primary diagnosis of hospital discharge was dizziness or vertigo according to the ICD-10 coding, treated between 1st January 2018 and 31st December 2018. In this study, data was collected from the Health Information System (HIS) of 131 hospitals around China, including 101 tertiary hospitals, 24 secondary hospitals, and 6 primary hospitals.

The specific inclusion criteria of the patients are:

  1. 1)

    Inpatient who diagnosed with dizziness or vertigo between 1st January 2018 and 31st December 2018;

  2. 2)

    Dizziness or vertigo was the principal diagnosis (ICD-10 code: H81 and R42);

  3. 3)

    Gastrodin injection alone or Extract of Ginkgo Biloba Leaves injection alone in clinical treatment.

The specific exclusion criteria of the patients are:

  1. 1)

    Patients who were younger than 18 years old or older than 75 years old;

  2. 2)

    Patients with cancers or pregnancy;

  3. 3)

    Patient record is incomplete.

Regarding patient inclusion, we selected the data in sequence. First, coding H81 and R42 with ICD-10 was used to filter and diagnose data containing H81 and R42 from the full data set to obtain the Per Protocol Set (PPS). Second, according to the subgroup design, the subgroup data was screened separately. The subgroup of dizziness and vertigo combined with cerebral infarction is a sub-data set filtered with the keyword “cerebral infarction” from PPS.

Sampling

The included patients were divided into two samples: sample of dizziness or vertigo; sample of dizziness or vertigo complicated with cerebral infarction.

  • Sample of dizziness or vertigo

    Patients were with the only principal diagnosis as dizziness or vertigo.

  • Sample of dizziness or vertigo, with the complication of cerebral infarction

    Patients were with the principal diagnosis as dizziness or vertigo, and with another diagnosis as cerebral infarction.

Treatment

All patients were divided into exposed group and control group. The exposed group was hospitalized with Gastrodin injection, and the control group was treated with Extract of Ginkgo Biloba Leaves injection. The outcomes and costs of Gastrodin injection and Extract of Ginkgo Biloba Leaves injection were compared.

  • Gastrodin injection

    During hospitalization, the principal diagnosis was dizziness or vertigo and was prescribed Gastrodin injection, while Extract of Ginkgo Biloba Leaves injection and other Chinese medicine injections of dizziness or vertigo were not prescribed.

  • Extract of Ginkgo Biloba Leaves injection

    During hospitalization, the principal diagnosis was dizziness or vertigo and was prescribed Extract of Ginkgo Biloba Leaves injection, while Gastrodin injection and other Chinese medicine injections of dizziness or vertigo were not prescribed.

Due to the lack of therapeutic dosage on the first page of the collected electronic health records, the therapeutic dosage could not be included in the analysis. The clinical experts we consulted indicated that clinicians usually chose therapeutic dosage according to patient status and disease progression in realistic practice. Thus, in this study, we compared the two groups (Gastrodin injection vs. Extract of Ginkgo Biloba Leaves injection), not the therapeutic dosage.

Outcomes

This study’s outcome indicators included medical cost per hospitalization, hospitalization duration, effective rate, and cure rate, which were suggested by the clinical experts we consulted. Therapeutic effects are divided into death, ineffective, effective (turn for the better, cure), and others. Specifically, effective includes turn for the better and cure of clinical treatment. Cure refers to “the cure of each hospitalization”, and the cure rate refers to “the cure rate of each hospitalization”. The cure rate is based on the realistic observation and judgment of clinical doctors directly responsible for the patients, which is directly extracted from the original medical records in the HIS of the hospitals.

Costs

In this study, the costs only considered the direct medical cost in the period of 1st January 2018 to 31st December 2018. Including total hospitalization costs, drug fees, laboratory fees, bed fees, operation fees, nursing fees, inspection fees, treatment fees, and other fees. Among them, the cost of drug includes target drug fee (Gastrodin injection or Extract of Ginkgo Biloba Leaves injection) and other drug fee. Cost data collected from HIS of 131 hospitals over the country. This study focused on medical costs per hospitalization because this data is the most reliable data to reflect treatments’ economic effectiveness.

Bias and elimination

Propensity score matching (PSM) is used to control the confounding factors and reduce the impact of confounding factors in evaluating intervention effects. In the study, logistic regression was used to score the tendency, mixed variables including region, hospital level, hospital department, age, and sex. PSM was achieved by Nearest Neighbor Matching (NNM) in the match it bag of R language, where the matching ratio is set to be 1:1.

Statistical analysis

In this study, descriptive statistics analysis was conducted to describe basic characteristics, comparative analysis of outcome, and cost. Descriptive analysis was conducted as measurement data are described by median and quartile, and enumeration data are described by frequency and rate. The outcome, hospitalization cost and composition, percentage, and P-value of the two groups were also compared and analyzed by SPSS statistical software. P < 0.05 was considered statistically significant.

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