Asynchronous class attribut value change but PageTab doesn refresh the value

Ionic Framework ionic-v3
1

I have Tabs built with start tabs project and inside one tab class home.ts I have:

export class HomePage implements OnInit, OnChanges, AfterViewInit, OnDestroy {
    // Show/Hide test
    test: number; /// now it is undefined
    (...)
    constructor(public navCtrl: NavController) {
        (...)
        this.test = 0;

        // Subscribe to some of the delegate's event handlers
        this.delegate.SomeAsynchronous()
            .subscribe(
                data => {
                    console.log('=== OK ===='+ this.test);
                     // the most important
                     this.test = 1;
                    console.log('=== OK ===='+ this.test);
                }, 
                (.... error.... )
             );   
    }

I have template home.html of this page where content is like this:

    {{test}}    
    <ion-card *ngIf="test > 0">
          (...)
    </ion-card>

And the test value changes asynchronusly I see this in the log but ion-card is not visible. BUT when I go to other tab and back to home it is visible but if asynchronusly back to 0 (from 1) nothing happen even I change the tab.

How to do that right? I mean how to change visibility of something in the tab after asynchronic changes?