Indonesia Has 270 Million People—and One of the World's Lowest Covid-19 Testing Rates

Mexico, seen as a low-testing country, has tested 13 out of 1,000 people—about 60% higher than Indonesia. India, which reports the number of samples tested rather than people tested, has done 60 tests per 1,000 people. That’s more than four times the number of samples per 1,000 people that Indonesia has reported testing.

The result: Policy makers and public-health experts in Indonesia—which with more than 11,000 deaths from Covid-19 has more than any country in East Asia—don’t quite know where and how widely the virus is spreading, making it much harder to contain the disease. Low testing also is an impediment to deciding when and where to restrict or reopen economic activity.

Countries use different methodologies to calculate national testing totals, so country-to-country figures may not be directly comparable. Nonetheless, they give a general indication of the degree to which different governments are tracking the pandemic.

In Indonesia, the paucity of proper testing also means that many people with Covid-19 aren’t getting diagnosed and don’t know when to isolate, exacerbating the spread of the illness, say public health experts.

In some cases, Indonesians hospitalized with Covid-19 symptoms are given rapid antibody blood tests that cannot reliably diagnose the disease, rather than saliva- or nasal-swab-based polymerase chain reaction tests, also known as PCR tests, that are considered the gold standard for diagnosis.

Yasha Chatab , an Indonesian tech-company director, said he rushed to the emergency room last month with a high fever. He was given an antibody test that came back negative and was prescribed antibiotics. He went back home, mainly keeping to his room, but still leaving to buy necessities. When his condition didn’t improve after a few days, he went to a medical clinic and this time got a PCR test, which came back positive three days later.

“It created a very large risk because it gave me a false sense of security,” Mr. Chatab said of the antibody test. “I wouldn’t have stepped out at all” if he had known that he was infected, he added

Nationally, only about 25,000 to 30,000 people in Indonesia receive PCR tests a day.

“It’s hard to be sure what is the correct course of action while at the same time doubting the data quality,” said Panji Hadisoemarto , an epidemiologist at Padjadjaran University in the city of Bandung who advises regional government officials on strategies for handling the outbreak. “We don’t have the data to prove or disprove any theories at the moment—that’s what’s most frustrating.”

Indonesia has reported just over 300,000 cases—similar to Germany, which has less than a third the population. One sign infections are being missed is that the more Indonesia tests, the more cases it finds.

Daily case-counts rose from 2,000 in early August to about 4,000 by late September—a period during which the number of tests a day also doubled. The rate of positive tests has remained fairly constant throughout, at around 15%. That is well above the rate that public health experts consider a warning that cases are going undiagnosed and more testing is needed.

The rise in cases prompted new restrictions in Jakarta, the capital, in mid-September, which the government says has helped bend the curve slightly. The restrictions limit the number of people who can be in offices and places of worship and require restaurants to offer takeout only.

Throughout the pandemic Indonesia has avoided nationwide lockdowns, although some regions have adopted restrictions on movement.

In guidelines released in July, the government said rapid tests—a term in Indonesia that mainly refers to antibody tests—shouldn’t be used for diagnosis. This type of test involves checking blood samples to see if patients produced antibodies in response to the virus.

These tests are processed relatively quickly, but usually are used to determine whether a person was infected in the past. They cannot reliably diagnose active Covid-19, doctors say, because it can take a week or more after the disease’s onset for people to generate antibodies, which means those with an early-stage illness often receive negative results.

As early as March, official guidance on antibody tests said all results should be confirmed using PCR. But availability of those tests remains low and distribution patchy.

Antibody tests aren’t counted in the nation’s total testing tally.

There is no one reason for Indonesia’s testing problem. Researchers and doctors variously blame shortages of trained laboratory personnel, difficulties in acquiring chemical reagents for test kits and a paucity of machines to process tests.

“They don’t know how to solve this problem,” said Pandu Riono , an infectious disease expert at the University of Indonesia, referring to the government.

The Indonesian health ministry didn’t respond to requests for comment. A government Covid-19 task force said in a posting last month that the country had been “quite successful” at increasing testing capacity while acknowledging that testing rates fell below World Health Organization standards.

Public health experts also say testing began with a misstep. In late March, President Joko Widodo called for a broad roll out of testing kits. The tests that hospitals and government bodies subsequently procured were in many cases antibody tests.

“We took the wrong first step,” said Dr. Tri Maharani, an emergency medicine specialist in Kediri, a city of 300,000 in East Java. When she fell ill after treating patients in June, she was given an antibody test, which came back negative. She received a PCR test the same day, and results five days later confirmed she had the virus, she said.

Few of the roughly 150 antibody tests administered at her hospital have come back positive, she said.

Dr. Maharani said the city has limited capacity to process PCR tests, with just one hospital possessing the appropriate machine. A representative for the hospital, Gambiran Kediri , said it could test 24 samples a day.

Dr. Maharani said she wears a hazmat suit to treat symptomatic patients without verifying if they are infected. The emergency room is like a “jungle,” she said, where doctors can’t be sure if someone has Covid-19.

Hers isn’t a designated hospital for the disease and she must refer suspected cases elsewhere, which requires an antibody test of the patient per hospital policy, she said. If the result is negative, she still tries to persuade doctors at referral hospitals to accept the patient based on his or her symptoms.

Dr. Maharani said the government should increase PCR testing, potentially using mobile clinics in rural areas. “The shortage has led to many silent cases,” she said.

Write to Jon Emont at jonathan.emont@wsj.com